diff --git a/client/src/components/dueDates/dueDatesTestData.ts b/client/src/components/dueDates/dueDatesTestData.ts
deleted file mode 100644
index fe14ff32..00000000
--- a/client/src/components/dueDates/dueDatesTestData.ts
+++ /dev/null
@@ -1,60 +0,0 @@
-import dayjs from "dayjs";
-
-export const dueDatesTestData = () => {
-  return [
-    {
-      id: 1,
-      start: dayjs("2023-06-14T15:00:00+02:00"),
-      end: dayjs("2023-06-14T18:00:00+02:00"),
-      title: "Präsenzkurs Kickoff",
-      url: "/course/überbetriebliche-kurse/learn/kickoff/präsenzkurs-kickoff",
-      course_session: 2,
-      page: 383,
-    },
-    {
-      id: 2,
-      start: dayjs("2023-06-15T15:00:00+02:00"),
-      end: dayjs("2023-06-15T18:00:00+02:00"),
-      title: "Präsenzkurs Basis",
-      url: "/course/überbetriebliche-kurse/learn/basis/präsenzkurs-basis",
-      course_session: 2,
-      page: 397,
-    },
-    {
-      id: 3,
-      start: dayjs("2023-06-16T15:00:00+02:00"),
-      end: dayjs("2023-06-16T18:00:00+02:00"),
-      title: "Präsenzkurs Fahrzeug",
-      url: "/course/überbetriebliche-kurse/learn/fahrzeug/präsenzkurs-fahrzeug",
-      course_session: 2,
-      page: 413,
-    },
-    {
-      id: 4,
-      start: dayjs("2023-06-16T15:00:00+02:00"),
-      end: dayjs("2023-06-16T18:00:00+02:00"),
-      title: "Präsenzkurs Flugzeuge",
-      url: "/course/überbetriebliche-kurse/learn/fahrzeug/präsenzkurs-fahrzeug",
-      course_session: 2,
-      page: 413,
-    },
-    {
-      id: 5,
-      start: dayjs("2023-07-16T11:00:00+02:00"),
-      end: dayjs("2023-07-16T18:00:00+02:00"),
-      title: "Präsenzkurs Motorräder",
-      url: "/course/überbetriebliche-kurse/learn/fahrzeug/präsenzkurs-fahrzeug",
-      course_session: 2,
-      page: 413,
-    },
-    {
-      id: 6,
-      start: dayjs("2023-08-09T15:00:00+02:00"),
-      end: dayjs("2023-08-09T19:00:00+02:00"),
-      title: "Präsenzkurs Fahrräder",
-      url: "/course/überbetriebliche-kurse/learn/fahrzeug/präsenzkurs-fahrzeug",
-      course_session: 2,
-      page: 413,
-    },
-  ];
-};
diff --git a/client/src/components/feedback/feedbackSummary.vue b/client/src/components/feedback/feedbackSummary.vue
index 967ba7cc..bccfa7bb 100644
--- a/client/src/components/feedback/feedbackSummary.vue
+++ b/client/src/components/feedback/feedbackSummary.vue
@@ -37,7 +37,7 @@ import { onMounted, ref, watch } from "vue";
 import type { Circle } from "@/services/circle";
 
 interface FeedbackSummary {
-  circle_id: number;
+  circle_id: string;
   count: number;
 }
 
@@ -65,7 +65,7 @@ function makeSummary(
 const props = defineProps<{
   selctedCircles: string[];
   circles: Circle[];
-  courseSessionId: number;
+  courseSessionId: string;
   url: string;
 }>();
 
diff --git a/client/src/components/header/AccountMenuContent.stories.ts b/client/src/components/header/AccountMenuContent.stories.ts
index 4b715451..4af4d2de 100644
--- a/client/src/components/header/AccountMenuContent.stories.ts
+++ b/client/src/components/header/AccountMenuContent.stories.ts
@@ -23,11 +23,11 @@ type Story = StoryObj<typeof AccountMenuContent>;
 
 const courseSessions = [
   {
-    id: 1,
+    id: "1",
     title: "Bern 2023 a",
   },
   {
-    id: 2,
+    id: "2",
     title: "Zürich 2023 a",
   },
 ];
diff --git a/client/src/components/header/AccountMenuContent.vue b/client/src/components/header/AccountMenuContent.vue
index 166ce523..91f12f17 100644
--- a/client/src/components/header/AccountMenuContent.vue
+++ b/client/src/components/header/AccountMenuContent.vue
@@ -6,7 +6,7 @@ import type { CourseSession } from "@/types";
 const props = defineProps<{
   courseSessions: CourseSession[];
   user: UserState;
-  selectedCourseSession?: number;
+  selectedCourseSession?: string;
 }>();
 
 const emit = defineEmits(["selectCourseSession", "logout"]);
diff --git a/client/src/components/header/CourseSessionsMenu.vue b/client/src/components/header/CourseSessionsMenu.vue
index 2212b07c..6aca1aee 100644
--- a/client/src/components/header/CourseSessionsMenu.vue
+++ b/client/src/components/header/CourseSessionsMenu.vue
@@ -36,7 +36,7 @@ export interface Item {
 
 export interface Props {
   items: CourseSession[];
-  selected?: number;
+  selected?: string;
 }
 
 const props = defineProps<Props>();
diff --git a/client/src/components/ui/ItDropdownSelect.vue b/client/src/components/ui/ItDropdownSelect.vue
index 9421c218..1897de01 100644
--- a/client/src/components/ui/ItDropdownSelect.vue
+++ b/client/src/components/ui/ItDropdownSelect.vue
@@ -20,7 +20,7 @@ const emit = defineEmits<{
 const props = withDefaults(defineProps<Props>(), {
   modelValue: () => {
     return {
-      id: -1,
+      id: "-1",
       name: "",
     };
   },
diff --git a/client/src/composables.ts b/client/src/composables.ts
index 36c70c78..e2a4d99c 100644
--- a/client/src/composables.ts
+++ b/client/src/composables.ts
@@ -33,14 +33,14 @@ export function useCurrentCourseSession() {
   return result;
 }
 
-export function useCourseSessionDetailQuery(courSessionId?: string | number) {
+export function useCourseSessionDetailQuery(courSessionId?: string) {
   if (!courSessionId) {
     courSessionId = useCurrentCourseSession().value.id;
   }
   const queryResult = useQuery({
     query: COURSE_SESSION_DETAIL_QUERY,
     variables: {
-      courseSessionId: courSessionId.toString(),
+      courseSessionId: courSessionId,
     },
   });
 
diff --git a/client/src/pages/AppointmentsPage.vue b/client/src/pages/AppointmentsPage.vue
index a5496775..1d26beb5 100644
--- a/client/src/pages/AppointmentsPage.vue
+++ b/client/src/pages/AppointmentsPage.vue
@@ -9,12 +9,12 @@ import DueDatesList from "@/components/dueDates/DueDatesList.vue";
 
 const { t } = useTranslation();
 
-const UNFILTERED = Number.MAX_SAFE_INTEGER;
+const UNFILTERED = Number.MAX_SAFE_INTEGER.toString();
 const courseSessionsStore = useCourseSessionsStore();
 const learningPathStore = useLearningPathStore();
 
 type Item = {
-  id: number;
+  id: string;
   name: string;
 };
 
@@ -108,7 +108,7 @@ const isMatchingCircle = (dueDate: DueDate) =>
   dueDate.circle?.id === selectedCircle.value.id;
 
 const isMatchingCourse = (dueDate: DueDate) =>
-  courseSessions.value.map((cs) => cs.id).includes(dueDate.course_session as number);
+  courseSessions.value.map((cs) => cs.id).includes(dueDate.course_session);
 
 const numAppointmentsToShow = ref(7);
 const canLoadMore = computed(() => {
diff --git a/client/src/pages/cockpit/assignmentEvaluationPage/AssignmentEvaluationPage.vue b/client/src/pages/cockpit/assignmentEvaluationPage/AssignmentEvaluationPage.vue
index b201d057..fd42b7c8 100644
--- a/client/src/pages/cockpit/assignmentEvaluationPage/AssignmentEvaluationPage.vue
+++ b/client/src/pages/cockpit/assignmentEvaluationPage/AssignmentEvaluationPage.vue
@@ -1,5 +1,5 @@
 <script setup lang="ts">
-import { useCurrentCourseSession, useCourseSessionDetailQuery } from "@/composables";
+import { useCourseSessionDetailQuery, useCurrentCourseSession } from "@/composables";
 import { ASSIGNMENT_COMPLETION_QUERY } from "@/graphql/queries";
 import EvaluationContainer from "@/pages/cockpit/assignmentEvaluationPage/EvaluationContainer.vue";
 import AssignmentSubmissionResponses from "@/pages/learningPath/learningContentPage/assignment/AssignmentSubmissionResponses.vue";
@@ -26,7 +26,7 @@ const router = useRouter();
 const queryResult = useQuery({
   query: ASSIGNMENT_COMPLETION_QUERY,
   variables: {
-    courseSessionId: courseSession.value.id.toString(),
+    courseSessionId: courseSession.value.id,
     assignmentId: props.assignmentId,
     assignmentUserId: props.userId,
   },
diff --git a/client/src/pages/cockpit/assignmentEvaluationPage/EvaluationIntro.vue b/client/src/pages/cockpit/assignmentEvaluationPage/EvaluationIntro.vue
index 19186c0a..89a174cf 100644
--- a/client/src/pages/cockpit/assignmentEvaluationPage/EvaluationIntro.vue
+++ b/client/src/pages/cockpit/assignmentEvaluationPage/EvaluationIntro.vue
@@ -27,9 +27,9 @@ async function startEvaluation() {
   log.debug("startEvaluation");
   if (props.assignmentCompletion.completion_status !== "EVALUATION_SUBMITTED") {
     upsertAssignmentCompletionMutation.executeMutation({
-      assignmentId: props.assignment.id.toString(),
-      courseSessionId: courseSession.value.id.toString(),
-      assignmentUserId: props.assignmentUser.user_id.toString(),
+      assignmentId: props.assignment.id,
+      courseSessionId: courseSession.value.id,
+      assignmentUserId: props.assignmentUser.user_id,
       completionStatus: "EVALUATION_IN_PROGRESS",
       completionDataString: JSON.stringify({}),
       // next line used for urql
diff --git a/client/src/pages/cockpit/assignmentEvaluationPage/EvaluationSummary.vue b/client/src/pages/cockpit/assignmentEvaluationPage/EvaluationSummary.vue
index 6fbfcdf1..db9cfe44 100644
--- a/client/src/pages/cockpit/assignmentEvaluationPage/EvaluationSummary.vue
+++ b/client/src/pages/cockpit/assignmentEvaluationPage/EvaluationSummary.vue
@@ -41,9 +41,9 @@ const upsertAssignmentCompletionMutation = useMutation(
 
 async function submitEvaluation() {
   upsertAssignmentCompletionMutation.executeMutation({
-    assignmentId: props.assignment.id.toString(),
-    courseSessionId: courseSession.value.id.toString(),
-    assignmentUserId: props.assignmentUser.user_id.toString(),
+    assignmentId: props.assignment.id,
+    courseSessionId: courseSession.value.id,
+    assignmentUserId: props.assignmentUser.user_id,
     completionStatus: "EVALUATION_SUBMITTED",
     completionDataString: JSON.stringify({}),
     evaluationPoints: userPoints.value,
diff --git a/client/src/pages/cockpit/assignmentEvaluationPage/EvaluationTask.vue b/client/src/pages/cockpit/assignmentEvaluationPage/EvaluationTask.vue
index e23242a7..f2c273dc 100644
--- a/client/src/pages/cockpit/assignmentEvaluationPage/EvaluationTask.vue
+++ b/client/src/pages/cockpit/assignmentEvaluationPage/EvaluationTask.vue
@@ -66,9 +66,9 @@ async function evaluateAssignmentCompletion(completionData: AssignmentCompletion
   log.debug("evaluateAssignmentCompletion", completionData);
 
   upsertAssignmentCompletionMutation.executeMutation({
-    assignmentId: props.assignment.id.toString(),
-    courseSessionId: courseSession.value.id.toString(),
-    assignmentUserId: props.assignmentUser.user_id.toString(),
+    assignmentId: props.assignment.id,
+    courseSessionId: courseSession.value.id,
+    assignmentUserId: props.assignmentUser.user_id,
     completionStatus: "EVALUATION_IN_PROGRESS",
     completionDataString: JSON.stringify(completionData),
     // eslint-disable-next-line @typescript-eslint/ban-ts-comment
diff --git a/client/src/pages/cockpit/cockpitPage/AssignmentSubmissionProgress.vue b/client/src/pages/cockpit/cockpitPage/AssignmentSubmissionProgress.vue
index 07d21712..66674d63 100644
--- a/client/src/pages/cockpit/cockpitPage/AssignmentSubmissionProgress.vue
+++ b/client/src/pages/cockpit/cockpitPage/AssignmentSubmissionProgress.vue
@@ -25,7 +25,7 @@ const state = reactive({
   statusByUser: [] as {
     userStatus: AssignmentCompletionStatus;
     progressStatus: StatusCountKey;
-    userId: number;
+    userId: string;
   }[],
   submissionProgressStatusCount: {} as StatusCount,
   gradingProgressStatusCount: {} as StatusCount,
diff --git a/client/src/pages/cockpit/cockpitPage/FeedbackSubmissionProgress.vue b/client/src/pages/cockpit/cockpitPage/FeedbackSubmissionProgress.vue
index b39dfe49..111e915f 100644
--- a/client/src/pages/cockpit/cockpitPage/FeedbackSubmissionProgress.vue
+++ b/client/src/pages/cockpit/cockpitPage/FeedbackSubmissionProgress.vue
@@ -8,7 +8,7 @@ import { useCourseSessionDetailQuery } from "@/composables";
 
 const props = defineProps<{
   courseSession: CourseSession;
-  circleId: number;
+  circleId: string;
 }>();
 
 log.debug("FeedbackSubmissionProgress created");
diff --git a/client/src/pages/cockpit/cockpitPage/SubmissionsOverview.vue b/client/src/pages/cockpit/cockpitPage/SubmissionsOverview.vue
index f53ecdc4..d9965814 100644
--- a/client/src/pages/cockpit/cockpitPage/SubmissionsOverview.vue
+++ b/client/src/pages/cockpit/cockpitPage/SubmissionsOverview.vue
@@ -16,7 +16,7 @@ import { learningContentTypeData } from "@/utils/typeMaps";
 import { useCourseSessionDetailQuery } from "@/composables";
 
 interface Submittable {
-  id: number;
+  id: string;
   circleName: string;
   frontendUrl: string;
   title: string;
@@ -27,7 +27,7 @@ interface Submittable {
 
 const props = defineProps<{
   courseSession: CourseSession;
-  selectedCircle: number;
+  selectedCircle: string;
 }>();
 
 log.debug("SubmissionsOverview created", props.courseSession.id);
diff --git a/client/src/pages/cockpit/documentPage/DocumentUploadForm.vue b/client/src/pages/cockpit/documentPage/DocumentUploadForm.vue
index 1fbe6452..1946b2f5 100644
--- a/client/src/pages/cockpit/documentPage/DocumentUploadForm.vue
+++ b/client/src/pages/cockpit/documentPage/DocumentUploadForm.vue
@@ -26,7 +26,7 @@ const formData = reactive<DocumentUploadData>({
   file: null,
   name: "",
   learningSequence: {
-    id: -1,
+    id: "-1",
     name: t("circlePage.documents.chooseSequence"),
   },
 });
@@ -56,7 +56,7 @@ function submitForm() {
 
 function validateForm() {
   formErrors.file = formData.file === null;
-  formErrors.learningSequence = formData.learningSequence.id === -1;
+  formErrors.learningSequence = formData.learningSequence.id === "-1";
   formErrors.name = formData.name === "";
 
   for (const [, value] of Object.entries(formErrors)) {
diff --git a/client/src/pages/competence/CompetenceCertificateDetailPage.vue b/client/src/pages/competence/CompetenceCertificateDetailPage.vue
index 54e2a2b3..43dd169c 100644
--- a/client/src/pages/competence/CompetenceCertificateDetailPage.vue
+++ b/client/src/pages/competence/CompetenceCertificateDetailPage.vue
@@ -20,7 +20,7 @@ const certificatesQuery = useQuery({
   query: COMPETENCE_NAVI_CERTIFICATE_QUERY,
   variables: {
     courseSlug: props.courseSlug,
-    courseSessionId: courseSession.value.id.toString(),
+    courseSessionId: courseSession.value.id,
   },
 });
 
diff --git a/client/src/pages/competence/CompetenceCertificateListPage.vue b/client/src/pages/competence/CompetenceCertificateListPage.vue
index 7d407425..c4c4157d 100644
--- a/client/src/pages/competence/CompetenceCertificateListPage.vue
+++ b/client/src/pages/competence/CompetenceCertificateListPage.vue
@@ -23,7 +23,7 @@ const certificatesQuery = useQuery({
   query: COMPETENCE_NAVI_CERTIFICATE_QUERY,
   variables: {
     courseSlug: props.courseSlug,
-    courseSessionId: courseSession.value.id.toString(),
+    courseSessionId: courseSession.value.id,
   },
 });
 
diff --git a/client/src/pages/competence/CompetenceIndexPage.vue b/client/src/pages/competence/CompetenceIndexPage.vue
index 54328354..87062ecf 100644
--- a/client/src/pages/competence/CompetenceIndexPage.vue
+++ b/client/src/pages/competence/CompetenceIndexPage.vue
@@ -27,7 +27,7 @@ const certificatesQuery = useQuery({
   query: COMPETENCE_NAVI_CERTIFICATE_QUERY,
   variables: {
     courseSlug: props.courseSlug,
-    courseSessionId: courseSession.value.id.toString(),
+    courseSessionId: courseSession.value.id,
   },
 });
 
diff --git a/client/src/pages/learningPath/learningContentPage/assignment/AssignmentSubmissionView.vue b/client/src/pages/learningPath/learningContentPage/assignment/AssignmentSubmissionView.vue
index 24c4f672..d132b180 100644
--- a/client/src/pages/learningPath/learningContentPage/assignment/AssignmentSubmissionView.vue
+++ b/client/src/pages/learningPath/learningContentPage/assignment/AssignmentSubmissionView.vue
@@ -19,9 +19,9 @@ import { useCircleStore } from "@/stores/circle";
 
 const props = defineProps<{
   assignment: Assignment;
-  learningContentId: number;
+  learningContentId: string;
   assignmentCompletion?: AssignmentCompletion;
-  courseSessionId: number;
+  courseSessionId: string;
   submissionDeadlineStart?: string;
 }>();
 
@@ -83,9 +83,9 @@ const onEditTask = (task: AssignmentTask) => {
 const onSubmit = async () => {
   try {
     await upsertAssignmentCompletionMutation.executeMutation({
-      assignmentId: props.assignment.id.toString(),
-      courseSessionId: courseSession.value.id.toString(),
-      learningContentId: props.learningContentId.toString(),
+      assignmentId: props.assignment.id,
+      courseSessionId: courseSession.value.id,
+      learningContentId: props.learningContentId,
       completionDataString: JSON.stringify({}),
       completionStatus: "SUBMITTED",
       // eslint-disable-next-line @typescript-eslint/ban-ts-comment
diff --git a/client/src/pages/learningPath/learningContentPage/assignment/AssignmentTaskView.vue b/client/src/pages/learningPath/learningContentPage/assignment/AssignmentTaskView.vue
index f698330e..3d25b001 100644
--- a/client/src/pages/learningPath/learningContentPage/assignment/AssignmentTaskView.vue
+++ b/client/src/pages/learningPath/learningContentPage/assignment/AssignmentTaskView.vue
@@ -16,8 +16,8 @@ import log from "loglevel";
 import { computed, reactive } from "vue";
 
 const props = defineProps<{
-  assignmentId: number;
-  learningContentId: number;
+  assignmentId: string;
+  learningContentId: string;
   task: AssignmentTask;
   assignmentCompletion?: AssignmentCompletion;
 }>();
@@ -33,9 +33,9 @@ const upsertAssignmentCompletionMutation = useMutation(
 async function upsertAssignmentCompletion(completion_data: AssignmentCompletionData) {
   try {
     await upsertAssignmentCompletionMutation.executeMutation({
-      assignmentId: props.assignmentId.toString(),
-      courseSessionId: courseSession.value.id.toString(),
-      learningContentId: props.learningContentId.toString(),
+      assignmentId: props.assignmentId,
+      courseSessionId: courseSession.value.id,
+      learningContentId: props.learningContentId,
       completionDataString: JSON.stringify(completion_data),
       completionStatus: "IN_PROGRESS",
       // eslint-disable-next-line @typescript-eslint/ban-ts-comment
diff --git a/client/src/pages/learningPath/learningContentPage/assignment/AssignmentView.vue b/client/src/pages/learningPath/learningContentPage/assignment/AssignmentView.vue
index 3e902acf..c4f7b27a 100644
--- a/client/src/pages/learningPath/learningContentPage/assignment/AssignmentView.vue
+++ b/client/src/pages/learningPath/learningContentPage/assignment/AssignmentView.vue
@@ -33,9 +33,9 @@ const props = defineProps<{
 const queryResult = useQuery({
   query: ASSIGNMENT_COMPLETION_QUERY,
   variables: {
-    courseSessionId: courseSession.value.id.toString(),
-    assignmentId: props.learningContent.content_assignment_id.toString(),
-    learningContentId: props.learningContent.id.toString(),
+    courseSessionId: courseSession.value.id,
+    assignmentId: props.learningContent.content_assignment_id,
+    learningContentId: props.learningContent.id,
   },
   pause: true,
 });
@@ -47,7 +47,7 @@ const upsertAssignmentCompletionMutation = useMutation(
 );
 
 const submissionDeadline = computed(() => {
-  return courseSessionDetailResult.findAssignment(props.learningContent.id.toString())
+  return courseSessionDetailResult.findAssignment(props.learningContent.id)
     ?.submission_deadline;
 });
 
@@ -122,9 +122,9 @@ const currentTask = computed(() => {
 const initUpsertAssignmentCompletion = async () => {
   try {
     await upsertAssignmentCompletionMutation.executeMutation({
-      assignmentId: props.learningContent.content_assignment_id.toString(),
-      courseSessionId: courseSession.value.id.toString(),
-      learningContentId: props.learningContent.id.toString(),
+      assignmentId: props.learningContent.content_assignment_id,
+      courseSessionId: courseSession.value.id,
+      learningContentId: props.learningContent.id,
       completionDataString: JSON.stringify({}),
       completionStatus: "IN_PROGRESS",
       // eslint-disable-next-line @typescript-eslint/ban-ts-comment
diff --git a/client/src/pages/learningPath/learningContentPage/blocks/EdoniqTestBlock.vue b/client/src/pages/learningPath/learningContentPage/blocks/EdoniqTestBlock.vue
index aabdf41f..a7b428e4 100644
--- a/client/src/pages/learningPath/learningContentPage/blocks/EdoniqTestBlock.vue
+++ b/client/src/pages/learningPath/learningContentPage/blocks/EdoniqTestBlock.vue
@@ -32,9 +32,9 @@ const courseSessionEdoniqTest = computed(() => {
 const queryResult = useQuery({
   query: ASSIGNMENT_COMPLETION_QUERY,
   variables: {
-    courseSessionId: courseSession.value.id.toString(),
-    assignmentId: props.content.content_assignment_id.toString(),
-    learningContentId: props.content.id.toString(),
+    courseSessionId: courseSession.value.id,
+    assignmentId: props.content.content_assignment_id,
+    learningContentId: props.content.id,
   },
 });
 
diff --git a/client/src/pages/learningPath/learningContentPage/feedback/FeedbackBlock.vue b/client/src/pages/learningPath/learningContentPage/feedback/FeedbackBlock.vue
index 563cad49..b8f599f2 100644
--- a/client/src/pages/learningPath/learningContentPage/feedback/FeedbackBlock.vue
+++ b/client/src/pages/learningPath/learningContentPage/feedback/FeedbackBlock.vue
@@ -192,8 +192,8 @@ function hasStepValidInput(stepNumber: number) {
 function mutateFeedback(data: FeedbackData, submit = false) {
   log.debug("mutate feedback", feedbackData);
   return executeMutation({
-    courseSessionId: courseSession.value.id.toString(),
-    learningContentId: props.content.id.toString(),
+    courseSessionId: courseSession.value.id,
+    learningContentId: props.content.id,
     data: data,
     submitted: submit,
   })
diff --git a/client/src/services/assignmentService.ts b/client/src/services/assignmentService.ts
index 2da28988..c9d96a90 100644
--- a/client/src/services/assignmentService.ts
+++ b/client/src/services/assignmentService.ts
@@ -28,9 +28,9 @@ export function calcLearningContentAssignments(learningPath?: LearningPath) {
 }
 
 export async function loadAssignmentCompletionStatusData(
-  assignmentId: number,
-  courseSessionId: number,
-  learningContentId: number
+  assignmentId: string,
+  courseSessionId: string,
+  learningContentId: string
 ) {
   const courseSessionDetailResult = useCourseSessionDetailQuery();
 
diff --git a/client/src/services/circle.ts b/client/src/services/circle.ts
index b42dcff7..a5b3c11b 100644
--- a/client/src/services/circle.ts
+++ b/client/src/services/circle.ts
@@ -121,7 +121,7 @@ export class Circle implements WagtailCircle {
   previousCircle?: Circle;
 
   constructor(
-    public readonly id: number,
+    public readonly id: string,
     public readonly slug: string,
     public readonly title: string,
     public readonly translation_key: string,
diff --git a/client/src/services/files.ts b/client/src/services/files.ts
index 54d9584d..c2ada811 100644
--- a/client/src/services/files.ts
+++ b/client/src/services/files.ts
@@ -7,7 +7,7 @@ type FileData = {
   url: string;
 };
 
-async function startFileUpload(fileData: DocumentUploadData, courseSessionId: number) {
+async function startFileUpload(fileData: DocumentUploadData, courseSessionId: string) {
   if (fileData === null || fileData.file === null) {
     return null;
   }
@@ -73,7 +73,7 @@ function handleUpload(url: string, options: RequestInit) {
 
 export async function uploadCircleDocument(
   data: DocumentUploadData,
-  courseSessionId: number,
+  courseSessionId: string,
   bustCacheUrlKey = ""
 ) {
   if (data.file === null) {
@@ -102,6 +102,6 @@ export async function deleteCircleDocument(documentId: string, bustCacheUrlKey =
   return result;
 }
 
-export async function fetchCourseSessionDocuments(courseSessionId: number) {
+export async function fetchCourseSessionDocuments(courseSessionId: string) {
   return itGetCached(`/api/core/document/list/${courseSessionId}/`);
 }
diff --git a/client/src/services/learningPath.ts b/client/src/services/learningPath.ts
index bd4c6bbb..7a905396 100644
--- a/client/src/services/learningPath.ts
+++ b/client/src/services/learningPath.ts
@@ -57,7 +57,7 @@ export class LearningPath implements WagtailLearningPath {
   }
 
   constructor(
-    public readonly id: number,
+    public readonly id: string,
     public readonly slug: string,
     public readonly title: string,
     public readonly translation_key: string,
diff --git a/client/src/stores/__tests__/courseSession.spec.ts b/client/src/stores/__tests__/courseSession.spec.ts
index dec82031..3eb09b7d 100644
--- a/client/src/stores/__tests__/courseSession.spec.ts
+++ b/client/src/stores/__tests__/courseSession.spec.ts
@@ -35,11 +35,11 @@ describe("CourseSession Store", () => {
     };
     courseSessions = [
       {
-        id: 1,
+        id: "1",
         created_at: "2021-05-11T10:00:00.000000Z",
         updated_at: "2023-05-11T10:00:00.000000Z",
         course: {
-          id: 1,
+          id: "1",
           title: "Test Course",
           category_name: "Test Category",
           slug: "test-course",
diff --git a/client/src/stores/competence.ts b/client/src/stores/competence.ts
index 4197a245..f4d229f4 100644
--- a/client/src/stores/competence.ts
+++ b/client/src/stores/competence.ts
@@ -58,7 +58,7 @@ export const useCompetenceStore = defineStore({
     },
     flatPerformanceCriteria(
       userId: string | undefined = undefined,
-      circleId: number | undefined = undefined
+      circleId: string | undefined = undefined
     ) {
       if (!userId) {
         const userStore = useUserStore();
diff --git a/client/src/stores/completion.ts b/client/src/stores/completion.ts
index 515d392a..72868026 100644
--- a/client/src/stores/completion.ts
+++ b/client/src/stores/completion.ts
@@ -12,7 +12,7 @@ export const useCompletionStore = defineStore({
   getters: {},
   actions: {
     async loadCourseSessionCompletionData(
-      courseSessionId: number,
+      courseSessionId: string,
       userId: string,
       reload = false
     ) {
@@ -31,7 +31,7 @@ export const useCompletionStore = defineStore({
     async markPage(
       page: BaseCourseWagtailPage,
       userId: string | undefined = undefined,
-      courseSessionId: number | undefined = undefined
+      courseSessionId: string | undefined = undefined
     ) {
       if (!courseSessionId) {
         const courseSessionsStore = useCourseSessionsStore();
diff --git a/client/src/stores/courseSessions.ts b/client/src/stores/courseSessions.ts
index ebfa3cb1..78f127e9 100644
--- a/client/src/stores/courseSessions.ts
+++ b/client/src/stores/courseSessions.ts
@@ -42,7 +42,7 @@ export const useCourseSessionsStore = defineStore("courseSessions", () => {
 
   const selectedCourseSessionMap = useLocalStorage(
     SELECTED_COURSE_SESSIONS_KEY,
-    new Map<string, number>()
+    new Map<string, string>()
   );
 
   const _currentCourseSlug = ref("");
@@ -84,13 +84,13 @@ export const useCourseSessionsStore = defineStore("courseSessions", () => {
     eventBus.emit("switchedCourseSession", courseSession.id);
   }
 
-  function getCourseSessionById(courseSessionId: number | string) {
+  function getCourseSessionById(courseSessionId: string) {
     return allCourseSessions.value.find((cs) => {
       return courseSessionId.toString() === cs.id.toString();
     });
   }
 
-  function switchCourseSessionById(courseSessionId: number | string) {
+  function switchCourseSessionById(courseSessionId: string) {
     const courseSession = allCourseSessions.value.find((cs) => {
       return courseSessionId.toString() === cs.id.toString();
     });
diff --git a/client/src/stores/user.ts b/client/src/stores/user.ts
index 7c2eee33..3ab6c207 100644
--- a/client/src/stores/user.ts
+++ b/client/src/stores/user.ts
@@ -26,7 +26,7 @@ export type UserState = {
   username: string;
   avatar_url: string;
   is_superuser: boolean;
-  course_session_experts: number[];
+  course_session_experts: string[];
   loggedIn: boolean;
   language: AvailableLanguages;
 };
diff --git a/client/src/types.ts b/client/src/types.ts
index 4a0015c2..921058a3 100644
--- a/client/src/types.ts
+++ b/client/src/types.ts
@@ -7,7 +7,7 @@ export type LoginMethod = "local" | "sso";
 export type CourseCompletionStatus = "UNKNOWN" | "FAIL" | "SUCCESS";
 
 export interface BaseCourseWagtailPage {
-  readonly id: number;
+  readonly id: string;
   readonly title: string;
   readonly slug: string;
   readonly content_type: string;
@@ -18,7 +18,7 @@ export interface BaseCourseWagtailPage {
 }
 
 export interface CircleLight {
-  readonly id: number;
+  readonly id: string;
   readonly slug: string;
   readonly title: string;
 }
@@ -52,10 +52,10 @@ export interface LearningContentInterface extends BaseCourseWagtailPage {
 
 export interface LearningContentAssignment extends LearningContentInterface {
   readonly content_type: "learnpath.LearningContentAssignment";
-  readonly content_assignment_id: number;
+  readonly content_assignment_id: string;
   readonly assignment_type: AssignmentType;
   readonly competence_certificate?: {
-    id: number;
+    id: string;
     title: string;
     slug: string;
     content_type: string;
@@ -104,9 +104,9 @@ export interface LearningContentEdoniqTest extends LearningContentInterface {
   readonly content_type: "learnpath.LearningContentEdoniqTest";
   readonly checkbox_text: string;
   readonly has_extended_time_test: boolean;
-  readonly content_assignment_id: number;
+  readonly content_assignment_id: string;
   readonly competence_certificate?: {
-    id: number;
+    id: string;
     title: string;
     slug: string;
     content_type: string;
@@ -191,22 +191,22 @@ export interface CourseCompletion {
   created_at: string;
   updated_at: string;
   readonly user: number;
-  readonly page_id: number;
+  readonly page_id: string;
   readonly page_type: string;
-  readonly course_session_id: number;
+  readonly course_session_id: string;
   completion_status: CourseCompletionStatus;
   additional_json_data: unknown;
 }
 
 export interface Course {
-  id: number;
+  id: string;
   title: string;
   category_name: string;
   slug: string;
 }
 
 export interface CourseCategory {
-  id: number;
+  id: string;
   name: string;
   general: boolean;
 }
@@ -381,7 +381,7 @@ export interface Assignment extends BaseCourseWagtailPage {
   readonly evaluation_tasks: AssignmentEvaluationTask[];
   readonly max_points: number;
   readonly competence_certificate?: {
-    id: number;
+    id: string;
     title: string;
     slug: string;
     content_type: string;
@@ -452,7 +452,7 @@ export interface CircleExpert {
   user_email: string;
   user_first_name: string;
   user_last_name: string;
-  circle_id: number;
+  circle_id: string;
   circle_slug: string;
   circle_translation_key: string;
 }
@@ -470,7 +470,7 @@ export interface CircleDocument {
 }
 
 export interface CourseSessionAttendanceCourse {
-  id: number;
+  id: string;
   due_date: SimpleDueDate;
   location: string;
   trainer: string;
@@ -498,7 +498,7 @@ export interface CourseSessionAssignment {
 
 export interface CourseSessionEdoniqTest {
   id: number;
-  course_session_id: number;
+  course_session_id: string;
   deadline: SimpleDueDate;
   learning_content: {
     id: string;
@@ -511,23 +511,14 @@ export interface CourseSessionEdoniqTest {
 }
 
 export interface CourseSession {
-  id: number;
+  id: string;
   created_at: string;
   updated_at: string;
   course: Course;
   title: string;
   start_date: string;
   end_date: string;
-  // learning_path_url: string;
-  // cockpit_url: string;
-  // competence_url: string;
   course_url: string;
-  // media_library_url: string;
-  // attendance_courses: CourseSessionAttendanceCourse[];
-  // assignments: CourseSessionAssignment[];
-  // edoniq_tests: CourseSessionEdoniqTest[];
-  // documents: CircleDocument[];
-  // users: CourseSessionUser[];
   due_dates: DueDate[];
 }
 
@@ -541,7 +532,7 @@ export interface CourseSessionUser {
   avatar_url: string;
   role: Role;
   circles: {
-    id: number;
+    id: string;
     title: string;
     slug: string;
     translation_key: string;
@@ -551,7 +542,7 @@ export interface CourseSessionUser {
 export interface ExpertSessionUser extends CourseSessionUser {
   role: "EXPERT";
   circles: {
-    id: number;
+    id: string;
     title: string;
     slug: string;
     translation_key: string;
@@ -577,7 +568,7 @@ export interface DocumentUploadData {
   file: File | null;
   name: string;
   learningSequence: {
-    id: number;
+    id: string;
     name: string;
   };
 }
@@ -647,8 +638,8 @@ export interface AssignmentCompletion {
 }
 
 export type UpsertUserAssignmentCompletion = {
-  assignment_id: number;
-  course_session_id: number;
+  assignment_id: string;
+  course_session_id: string;
   completion_status: AssignmentCompletionStatus;
   completion_data: AssignmentCompletionData;
 };
@@ -665,11 +656,11 @@ export interface UserAssignmentCompletionStatus {
   assignment_user_id: string;
   completion_status: AssignmentCompletionStatus;
   evaluation_points: number | null;
-  learning_content_page_id: number;
+  learning_content_page_id: string;
 }
 
 export type SimpleDueDate = {
-  id: number;
+  id: string;
   start: string;
   end?: string;
 };
@@ -681,7 +672,5 @@ export type DueDate = SimpleDueDate & {
   subtitle: string;
   url: string;
   url_expert: string;
-  course_session: number | null;
-  page: number | null;
   circle: CircleLight | null;
 };
diff --git a/client/src/utils/eventBus.ts b/client/src/utils/eventBus.ts
index 280e4a81..99689f1f 100644
--- a/client/src/utils/eventBus.ts
+++ b/client/src/utils/eventBus.ts
@@ -3,7 +3,7 @@ import mitt from "mitt";
 export type MittEvents = {
   // event needed so that the App components do re-render
   // and reload the current course session
-  switchedCourseSession: number;
+  switchedCourseSession: string;
 
   finishedLearningContent: boolean;
 };
diff --git a/server/vbv_lernwelt/core/utils.py b/server/vbv_lernwelt/core/utils.py
index e2a012fa..083ed57c 100644
--- a/server/vbv_lernwelt/core/utils.py
+++ b/server/vbv_lernwelt/core/utils.py
@@ -2,6 +2,7 @@ import json
 import re
 
 from django.utils.safestring import mark_safe
+from rest_framework import serializers
 from rest_framework.throttling import UserRateThrottle
 
 
@@ -41,6 +42,11 @@ def get_django_content_type(obj):
     return obj._meta.app_label + "." + type(obj).__name__
 
 
+class StringIDField(serializers.Field):
+    def to_representation(self, value):
+        return str(value)
+
+
 def pretty_print_json(json_string):
     try:
         parsed = json_string
diff --git a/server/vbv_lernwelt/course/serializer_helpers.py b/server/vbv_lernwelt/course/serializer_helpers.py
index a188f7f3..cfeba369 100644
--- a/server/vbv_lernwelt/course/serializer_helpers.py
+++ b/server/vbv_lernwelt/course/serializer_helpers.py
@@ -4,9 +4,11 @@ from vbv_lernwelt.core.serializer_helpers import (
     get_it_serializer_class,
     ItWagtailBaseSerializer,
 )
+from vbv_lernwelt.core.utils import StringIDField
 
 
 class CourseBaseSerializer(ItWagtailBaseSerializer):
+    id = StringIDField()
     course = SerializerMethodField()
     course_category = SerializerMethodField()
     circles = SerializerMethodField()
diff --git a/server/vbv_lernwelt/course/serializers.py b/server/vbv_lernwelt/course/serializers.py
index 2fc27dbd..c647ab3a 100644
--- a/server/vbv_lernwelt/course/serializers.py
+++ b/server/vbv_lernwelt/course/serializers.py
@@ -1,5 +1,6 @@
 from rest_framework import serializers
 
+from vbv_lernwelt.core.utils import StringIDField
 from vbv_lernwelt.course.models import (
     CircleDocument,
     Course,
@@ -12,6 +13,8 @@ from vbv_lernwelt.duedate.serializers import DueDateSerializer
 
 
 class CourseSerializer(serializers.ModelSerializer):
+    id = StringIDField()
+
     class Meta:
         model = Course
         fields = ["id", "title", "category_name", "slug"]
@@ -28,6 +31,9 @@ class CourseCategorySerializer(serializers.ModelSerializer):
 
 
 class CourseCompletionSerializer(serializers.ModelSerializer):
+    page_id = StringIDField()
+    course_session_id = StringIDField()
+
     class Meta:
         model = CourseCompletion
         fields = [
@@ -44,17 +50,10 @@ class CourseCompletionSerializer(serializers.ModelSerializer):
 
 
 class CourseSessionSerializer(serializers.ModelSerializer):
+    id = StringIDField()
+
     course = serializers.SerializerMethodField()
     course_url = serializers.SerializerMethodField()
-    # learning_path_url = serializers.SerializerMethodField()
-    # cockpit_url = serializers.SerializerMethodField()
-    # competence_url = serializers.SerializerMethodField()
-    # media_library_url = serializers.SerializerMethodField()
-    # documents = serializers.SerializerMethodField()
-    # attendance_courses = serializers.SerializerMethodField()
-    # assignments = serializers.SerializerMethodField()
-    # edoniq_tests = serializers.SerializerMethodField()
-
     due_dates = serializers.SerializerMethodField()
 
     def get_course(self, obj):
@@ -107,11 +106,11 @@ class CircleDocumentSerializer(serializers.ModelSerializer):
         circle = ls.get_circle()
         return {
             "title": ls.title,
-            "id": ls.id,
+            "id": str(ls.id),
             "slug": ls.slug,
             "circle": {
                 "title": circle.title,
-                "id": circle.id,
+                "id": str(circle.id),
                 "slug": circle.slug,
             },
         }
diff --git a/server/vbv_lernwelt/course_session/serializers.py b/server/vbv_lernwelt/course_session/serializers.py
index 7bec74a2..8b137891 100644
--- a/server/vbv_lernwelt/course_session/serializers.py
+++ b/server/vbv_lernwelt/course_session/serializers.py
@@ -1,82 +1 @@
-from rest_framework import serializers
 
-from vbv_lernwelt.course_session.models import (
-    CourseSessionAssignment,
-    CourseSessionAttendanceCourse,
-    CourseSessionEdoniqTest,
-)
-
-
-class CourseSessionAttendanceCourseSerializer(serializers.ModelSerializer):
-    start = serializers.SerializerMethodField()
-    end = serializers.SerializerMethodField()
-    circle_title = serializers.SerializerMethodField()
-
-    class Meta:
-        model = CourseSessionAttendanceCourse
-        fields = [
-            "id",
-            "course_session",
-            "learning_content_id",
-            "due_date_id",
-            "location",
-            "trainer",
-            "start",
-            "end",
-            "circle_title",
-        ]
-
-    def get_start(self, obj):
-        return obj.due_date.start
-
-    def get_end(self, obj):
-        return obj.due_date.end
-
-    def get_circle_title(self, obj):
-        circle = obj.get_circle()
-        if circle:
-            return circle.title
-        return ""
-
-
-class CourseSessionAssignmentSerializer(serializers.ModelSerializer):
-    submission_deadline_start = serializers.SerializerMethodField()
-    evaluation_deadline_start = serializers.SerializerMethodField()
-
-    class Meta:
-        model = CourseSessionAssignment
-        fields = [
-            "id",
-            "course_session_id",
-            "learning_content_id",
-            "submission_deadline_id",
-            "submission_deadline_start",
-            "evaluation_deadline_id",
-            "evaluation_deadline_start",
-        ]
-
-    def get_evaluation_deadline_start(self, obj):
-        if obj.evaluation_deadline:
-            return obj.evaluation_deadline.start
-
-    def get_submission_deadline_start(self, obj):
-        if obj.submission_deadline:
-            return obj.submission_deadline.start
-
-
-class CourseSessionEdoniqTestSerializer(serializers.ModelSerializer):
-    deadline_start = serializers.SerializerMethodField()
-
-    class Meta:
-        model = CourseSessionEdoniqTest
-        fields = [
-            "id",
-            "course_session_id",
-            "learning_content_id",
-            "deadline_id",
-            "deadline_start",
-        ]
-
-    def get_deadline_start(self, obj):
-        if obj.deadline:
-            return obj.deadline.start
diff --git a/server/vbv_lernwelt/duedate/serializers.py b/server/vbv_lernwelt/duedate/serializers.py
index 11a2734b..a7ab81f6 100644
--- a/server/vbv_lernwelt/duedate/serializers.py
+++ b/server/vbv_lernwelt/duedate/serializers.py
@@ -1,14 +1,20 @@
 from rest_framework import serializers
 
+from vbv_lernwelt.core.utils import StringIDField
 from vbv_lernwelt.duedate.models import DueDate
 
 
 class DueDateSerializer(serializers.ModelSerializer):
-    # circle = serializers.SerializerMethodField()
+    id = StringIDField()
+    circle = serializers.SerializerMethodField()
+
+    # course_session = StringIDField()
+    # page = StringIDField()
 
     class Meta:
         model = DueDate
         fields = [
+            "id",
             "start",
             "end",
             "manual_override_fields",
@@ -20,7 +26,7 @@ class DueDateSerializer(serializers.ModelSerializer):
             "url_expert",
             "course_session",
             "page",
-            # "circle",
+            "circle",
         ]
 
     def get_circle(self, obj):
@@ -28,7 +34,7 @@ class DueDateSerializer(serializers.ModelSerializer):
 
         if circle:
             return {
-                "id": circle.id,
+                "id": str(circle.id),
                 "title": circle.title,
                 "translation_key": circle.translation_key,
             }
diff --git a/server/vbv_lernwelt/learnpath/serializers.py b/server/vbv_lernwelt/learnpath/serializers.py
index 510d697a..3f6a3255 100644
--- a/server/vbv_lernwelt/learnpath/serializers.py
+++ b/server/vbv_lernwelt/learnpath/serializers.py
@@ -64,7 +64,7 @@ class LearningContentEdoniqTestSerializer(
         try:
             cert = obj.content_assignment.competence_certificate
             return {
-                "id": cert.id,
+                "id": str(cert.id),
                 "title": cert.title,
                 "slug": cert.slug,
                 "content_type": get_django_content_type(cert),
@@ -89,7 +89,7 @@ class LearningContentAssignmentSerializer(
         try:
             cert = obj.content_assignment.competence_certificate
             return {
-                "id": cert.id,
+                "id": str(cert.id),
                 "title": cert.title,
                 "slug": cert.slug,
                 "content_type": get_django_content_type(cert),