diff --git a/client/src/components/circle/CircleDiagram.vue b/client/src/components/circle/CircleDiagram.vue
index c40ec640..4845a4f2 100644
--- a/client/src/components/circle/CircleDiagram.vue
+++ b/client/src/components/circle/CircleDiagram.vue
@@ -1,10 +1,10 @@
 <script setup lang="ts">
 import * as d3 from "d3";
-import {computed, onMounted} from "vue";
+import {computed} from "vue";
 import * as _ from 'underscore'
+import {useCircleStore} from '@/stores/circle';
 
 const props = defineProps<{
-  circleStore: {},
   width: {
     default: 500,
     type: number,
@@ -18,28 +18,26 @@ const props = defineProps<{
   },
 }>()
 
+const circleStore = useCircleStore();
 
 function someFinished(learningSequence) {
-  return props.circleStore.flatChildren.filter((lc) => {
-    return lc.completed && lc.parentLearningSequence?.translation_key === learningSequence.translation_key;
-  }).length > 0;
+  if (circleStore.circle) {
+    return circleStore.circle.someFinishedInLearningSequence(learningSequence.translation_key);
+  }
+  return false;
 }
 
 
 const pieData = computed(() => {
-  const circle = props.circleStore.circleData, completionData = props.circleStore.completionData
-  console.log('initial of compute pie data ', circle, completionData)
+  const circle = circleStore.circle
+  console.log('initial of compute pie data ', circle)
 
-  if (circle && completionData) {
-    console.log('initial of compute pie data ', circle, completionData)
+  if (circle) {
+    console.log('initial of compute pie data ', circle)
     let learningSequences = _.filter(circle.children, (child) => {
       return child.type === 'learnpath.LearningSequence';
     })
 
-    const completionDataByPageId = _.object(_.map(completionData, function (item) {
-      return [item.page_key, item]
-    }))
-
     let pieWeights = new Array(Math.max(learningSequences.length, 1)).fill(1)
     let pieGenerator = d3.pie()
     let angles = pieGenerator(pieWeights)
diff --git a/client/src/components/circle/CircleOverview.vue b/client/src/components/circle/CircleOverview.vue
index 7a9b446a..29bf5ec5 100644
--- a/client/src/components/circle/CircleOverview.vue
+++ b/client/src/components/circle/CircleOverview.vue
@@ -1,8 +1,8 @@
 <script setup lang="ts">
-import type {Circle} from '@/types';
+import {Circle} from '@/services/circle';
 
 const props = defineProps<{
-  circleData: Circle
+  circle: Circle
 }>()
 
 </script>
@@ -17,7 +17,7 @@ const props = defineProps<{
     </div>
 
 
-    <h1 class="">Überblick: Circle "{{ circleData.title }}"</h1>
+    <h1 class="">Überblick: Circle "{{ circle.title }}"</h1>
 
     <p class="mt-8 text-xl">Hier zeigen wir dir, was du in diesem Circle lernen wirst.</p>
 
@@ -25,7 +25,7 @@ const props = defineProps<{
       <h3>Du wirst in der Lage sein, ... </h3>
 
       <ul class="mt-4">
-        <li class="text-xl flex items-center" v-for="goal in circleData.goals" :key="goal.id">
+        <li class="text-xl flex items-center" v-for="goal in circle.goals" :key="goal.id">
           <it-icon-check class="mt-4 hidden lg:block w-12 h-12 text-sky-500 flex-none"></it-icon-check>
           <div class="mt-4">{{ goal.value }}</div>
         </li>
@@ -38,7 +38,7 @@ const props = defineProps<{
 
     <ul class="grid grid-cols-1 lg:grid-cols-3 auto-rows-fr gap-6 mt-8">
       <li
-        v-for="jobSituation in circleData.job_situations"
+        v-for="jobSituation in circle.job_situations"
         :key="jobSituation.id"
         class="job-situation border border-gray-500 p-4 text-xl flex items-center"
       >
diff --git a/client/src/components/circle/LearningSequence.vue b/client/src/components/circle/LearningSequence.vue
index 91c2b5c5..a2578260 100644
--- a/client/src/components/circle/LearningSequence.vue
+++ b/client/src/components/circle/LearningSequence.vue
@@ -15,10 +15,8 @@ function toggleCompleted(learningContent: LearningContent) {
 }
 
 const someFinished = computed(() => {
-  if (props.learningSequence) {
-    return circleStore.flatChildren.filter((lc) => {
-      return lc.completed && lc.parentLearningSequence?.translation_key === props.learningSequence.translation_key;
-    }).length > 0;
+  if (props.learningSequence && circleStore.circle) {
+    return circleStore.circle.someFinishedInLearningSequence(props.learningSequence.translation_key);
   }
 
   return false;
diff --git a/client/src/services/circle.ts b/client/src/services/circle.ts
index 3cb8c462..acb460a9 100644
--- a/client/src/services/circle.ts
+++ b/client/src/services/circle.ts
@@ -1,4 +1,13 @@
-import type {CircleChild, LearningContent, LearningSequence, LearningUnit} from '@/types';
+import type {
+  CircleChild,
+  CircleCompletion,
+  CircleGoal,
+  CircleInterface,
+  CircleJobSituation,
+  LearningContent,
+  LearningSequence,
+  LearningUnit
+} from '@/types';
 
 
 function _createEmptyLearningUnit(parentLearningSequence: LearningSequence): LearningUnit {
@@ -98,3 +107,74 @@ export function parseLearningSequences (children: CircleChild[]): LearningSequen
   return result;
 }
 
+export class Circle implements CircleInterface {
+  readonly type = 'learnpath.Circle';
+  readonly learningSequences: LearningSequence[];
+  readonly completed: boolean;
+
+  constructor(
+    public readonly id: number,
+    public readonly slug: string,
+    public readonly title: string,
+    public readonly translation_key: string,
+    public description: string,
+    public children: CircleChild[],
+    public goals: CircleGoal[],
+    public job_situations: CircleJobSituation[],
+  ) {
+    this.learningSequences = parseLearningSequences(this.children);
+    this.completed = false;
+  }
+
+  public static fromJson(json: any): Circle {
+    // TODO add error checking when the data does not conform to the schema
+    return new Circle(
+      json.id,
+      json.slug,
+      json.title,
+      json.translation_key,
+      json.description,
+      json.children,
+      json.goals,
+      json.job_situations,
+    )
+  }
+
+  public get flatChildren(): CircleChild[] {
+    const result: CircleChild[] = [];
+    this.learningSequences.forEach((learningSequence) => {
+      learningSequence.learningUnits.forEach((learningUnit) => {
+        learningUnit.children.forEach((learningUnitQuestion) => {
+          result.push(learningUnitQuestion);
+        })
+        learningUnit.learningContents.forEach((learningContent) => {
+          result.push(learningContent);
+        });
+      });
+    });
+    return result;
+  }
+
+  public someFinishedInLearningSequence(translationKey: string): boolean {
+    if (translationKey) {
+      return this.flatChildren.filter((lc) => {
+        return lc.completed && lc.parentLearningSequence?.translation_key === translationKey;
+      }).length > 0;
+    }
+
+    return false;
+  }
+
+  public parseCompletionData(completionData: CircleCompletion[]) {
+    this.flatChildren.forEach((page) => {
+      const pageIndex = completionData.findIndex((e) => {
+        return e.page_key === page.translation_key;
+      });
+      if (pageIndex >= 0) {
+        page.completed = completionData[pageIndex].completed;
+      } else {
+        page.completed = undefined;
+      }
+    });
+  }
+}
diff --git a/client/src/stores/circle.ts b/client/src/stores/circle.ts
index cd5b1917..a3474604 100644
--- a/client/src/stores/circle.ts
+++ b/client/src/stores/circle.ts
@@ -2,14 +2,13 @@ import * as log from 'loglevel';
 
 import {defineStore} from 'pinia'
 
-import type {Circle, CircleChild, CircleCompletion, LearningContent, LearningUnit, LearningUnitQuestion} from '@/types'
+import type {LearningContent, LearningUnit, LearningUnitQuestion} from '@/types'
+import {Circle} from '@/services/circle'
 import {itGet, itPost} from '@/fetchHelpers';
-import {parseLearningSequences} from '@/services/circle';
 import {useAppStore} from '@/stores/app';
 
 export type CircleStoreState = {
-  circleData: Circle;
-  completionData: CircleCompletion[];
+  circle: Circle | undefined;
   currentLearningContent: LearningContent | undefined;
   currentSelfEvaluation: LearningUnit | undefined;
   page: 'INDEX' | 'OVERVIEW' | 'LEARNING_CONTENT' | 'SELF_EVALUATION';
@@ -19,7 +18,7 @@ export const useCircleStore = defineStore({
   id: 'circle',
   state: () => {
     return {
-      circleData: {},
+      circle: undefined,
       completionData: {},
       currentLearningContent: undefined,
       currentSelfEvaluation: undefined,
@@ -28,27 +27,15 @@ export const useCircleStore = defineStore({
   },
   getters: {
     flatChildren: (state) => {
-      const result:CircleChild[] = [];
-      state.circleData.learningSequences.forEach((learningSequence) => {
-        learningSequence.learningUnits.forEach((learningUnit) => {
-          learningUnit.children.forEach((learningUnitQuestion) => {
-            result.push(learningUnitQuestion);
-          })
-          learningUnit.learningContents.forEach((learningContent) => {
-            result.push(learningContent);
-          });
-        });
-      });
-      return result;
     },
   },
   actions: {
     async loadCircle(slug: string) {
       try {
-        this.circleData = await itGet(`/learnpath/api/circle/${slug}/`);
-        this.circleData.learningSequences = parseLearningSequences(this.circleData.children);
-        this.completionData = await itGet(`/api/completion/circle/${this.circleData.translation_key}/`);
-        this.parseCompletionData();
+        const circleData = await itGet(`/learnpath/api/circle/${slug}/`);
+        this.circle = Circle.fromJson(circleData);
+        const completionData = await itGet(`/api/completion/circle/${this.circle.translation_key}/`);
+        this.circle.parseCompletionData(completionData);
       } catch (error) {
         log.error(error);
         return error
@@ -57,28 +44,18 @@ export const useCircleStore = defineStore({
     async markCompletion(page: LearningContent | LearningUnitQuestion, flag = true) {
       try {
         page.completed = flag;
-        this.completionData = await itPost('/api/completion/circle/mark/', {
+        const completionData = await itPost('/api/completion/circle/mark/', {
           page_key: page.translation_key,
           completed: page.completed,
         });
-        this.parseCompletionData();
+        if (this.circle) {
+          this.circle.parseCompletionData(completionData);
+        }
       } catch (error) {
         log.error(error);
         return error
       }
     },
-    parseCompletionData() {
-      this.flatChildren.forEach((page) => {
-        const pageIndex = this.completionData.findIndex((e) => {
-          return e.page_key === page.translation_key;
-        });
-        if (pageIndex >= 0) {
-          page.completed = this.completionData[pageIndex].completed;
-        } else {
-          page.completed = undefined;
-        }
-      });
-    },
     openLearningContent(learningContent: LearningContent) {
       this.currentLearningContent = learningContent;
       const appStore = useAppStore();
diff --git a/client/src/types.ts b/client/src/types.ts
index 006b1d25..01dbae35 100644
--- a/client/src/types.ts
+++ b/client/src/types.ts
@@ -1,3 +1,5 @@
+import {parseLearningSequences} from '@/services/circle';
+
 export interface LearningContentBlock {
   type: 'web-based-training' | 'competence' | 'exercise' | 'knowledge';
   value: {
@@ -46,10 +48,10 @@ export interface CircleJobSituation {
 }
 
 export interface LearningWagtailPage {
-  id: number;
-  title: string;
-  slug: string;
-  translation_key: string;
+  readonly id: number;
+  readonly title: string;
+  readonly slug: string;
+  readonly translation_key: string;
   completed?: boolean;
 }
 
@@ -105,15 +107,17 @@ export interface CircleCompletion {
   json_data: any;
 }
 
-export interface Circle extends LearningWagtailPage {
-  type: 'learnpath.Circle';
-  children: CircleChild[];
-  description: string;
+export interface CircleInterface extends LearningWagtailPage {
+  readonly type: 'learnpath.Circle';
+  readonly children: CircleChild[];
+  readonly description: string;
+  readonly goals: CircleGoal[];
+  readonly job_situations: CircleJobSituation[];
   learningSequences: LearningSequence[];
-  goals: CircleGoal[];
-  job_situations: CircleJobSituation[];
 }
 
+
+
 export interface CircleDiagramData  {
           index: number
           title:  string
diff --git a/client/src/views/CircleView.vue b/client/src/views/CircleView.vue
index 7d07b4f2..c310d8e0 100644
--- a/client/src/views/CircleView.vue
+++ b/client/src/views/CircleView.vue
@@ -35,15 +35,15 @@ onMounted(async () => {
     <div v-else-if="circleStore.page === 'SELF_EVALUATION'">
       <SelfEvaluation :key="circleStore.currentSelfEvaluation.translation_key"/>
     </div>
-    <div v-else>
+    <div v-else-if="circleStore.circle">
       <div class="circle">
         <div class="flex flex-col lg:flex-row">
           <div class="flex-initial lg:w-128 px-4 py-4 lg:px-8 lg:py-8">
             <h1 class="text-blue-dark text-7xl">
-              {{ circleStore.circleData.title }}
+              {{ circleStore.circle.title }}
             </h1>
 
-            <div v-if="circleStore.circleData.learningSequences && circleStore.flatChildren" class="w-full mt-8">
+            <div v-if="circleStore.circle.learningSequences && circleStore.circle.flatChildren" class="w-full mt-8">
               <CircleDiagram :circle-store="circleStore"></CircleDiagram>
             </div>
 
@@ -65,7 +65,7 @@ onMounted(async () => {
               <div class="block border border-gray-500 mt-8 p-6">
                 <h3 class="text-blue-dark">Das lernst du in diesem Circle.</h3>
                 <div class="prose mt-4">
-                  {{ circleStore.circleData.description }}
+                  {{ circleStore.circle.description }}
                 </div>
 
                 <button class="btn-primary mt-4" @click="circleStore.page = 'OVERVIEW'">Erfahre mehr dazu</button>
@@ -83,12 +83,11 @@ onMounted(async () => {
 
           <div class="flex-auto bg-gray-100 px-4 py-8 lg:px-24">
             <div
-              v-for="learningSequence in circleStore.circleData.learningSequences"
+              v-for="learningSequence in circleStore.circle.learningSequences"
               :key="learningSequence.translation_key"
             >
               <LearningSequence
                 :learning-sequence="learningSequence"
-                :completion-data="circleStore.completionData"
               ></LearningSequence>
             </div>