diff --git a/backend/src/middleware/auth/checks/assignment-auth-checks.ts b/backend/src/middleware/auth/checks/assignment-auth-checks.ts
index 11199bb1..070df4a0 100644
--- a/backend/src/middleware/auth/checks/assignment-auth-checks.ts
+++ b/backend/src/middleware/auth/checks/assignment-auth-checks.ts
@@ -1,5 +1,4 @@
 import {authorize} from "./auth-checks";
-import {fetchAssignment} from "../../../services/assignments";
 import {fetchClass} from "../../../services/classes";
 import {fetchAllGroups} from "../../../services/groups";
 import {mapToUsername} from "../../../interfaces/user";
@@ -16,9 +15,9 @@ export const onlyAllowIfHasAccessToAssignment = authorize(
         if (auth.accountType === "teacher") {
             const clazz = await fetchClass(classId);
             return clazz.teachers.map(mapToUsername).includes(auth.username);
-        } else {
+        } 
             const groups = await fetchAllGroups(classId, assignmentId);
             return groups.some(group => group.members.map((member) => member.username).includes(auth.username) );
-        }
+        
     }
 );
diff --git a/backend/src/middleware/auth/checks/class-auth-checks.ts b/backend/src/middleware/auth/checks/class-auth-checks.ts
index 1f8e685b..603142be 100644
--- a/backend/src/middleware/auth/checks/class-auth-checks.ts
+++ b/backend/src/middleware/auth/checks/class-auth-checks.ts
@@ -1,7 +1,7 @@
 import {authorize} from "./auth-checks";
 import {AuthenticationInfo} from "../authentication-info";
 import {AuthenticatedRequest} from "../authenticated-request";
-import {fetchClass, getClass} from "../../../services/classes";
+import {fetchClass} from "../../../services/classes";
 import {mapToUsername} from "../../../interfaces/user";
 
 async function teaches(teacherUsername: string, classId: string): Promise<boolean> {
diff --git a/backend/src/middleware/auth/checks/group-auth-checker.ts b/backend/src/middleware/auth/checks/group-auth-checker.ts
index 73df4fb5..643a3713 100644
--- a/backend/src/middleware/auth/checks/group-auth-checker.ts
+++ b/backend/src/middleware/auth/checks/group-auth-checker.ts
@@ -1,6 +1,6 @@
 import {authorize} from "./auth-checks";
-import {fetchClass, getClass} from "../../../services/classes";
-import {fetchGroup, getGroup} from "../../../services/groups";
+import {fetchClass} from "../../../services/classes";
+import {fetchGroup} from "../../../services/groups";
 import {mapToUsername} from "../../../interfaces/user";
 
 /**
@@ -17,9 +17,9 @@ export const onlyAllowIfHasAccessToGroup = authorize(
         if (auth.accountType === "teacher") {
             const clazz = await fetchClass(classId);
             return clazz.teachers.map(mapToUsername).includes(auth.username);
-        } else { // user is student
+        }  // User is student
             const group = await fetchGroup(classId, assignmentId, groupId);
             return group.members.map(mapToUsername).includes(auth.username);
-        }
+        
     }
 );
diff --git a/backend/src/middleware/auth/checks/learning-content-auth-checks.ts b/backend/src/middleware/auth/checks/learning-content-auth-checks.ts
index 64d78c73..a13cd038 100644
--- a/backend/src/middleware/auth/checks/learning-content-auth-checks.ts
+++ b/backend/src/middleware/auth/checks/learning-content-auth-checks.ts
@@ -1,7 +1,6 @@
 import {authorize} from "./auth-checks";
 import {AuthenticationInfo} from "../authentication-info";
 import {AuthenticatedRequest} from "../authenticated-request";
-import {fetchGroup, getGroup} from "../../../services/groups";
 
 /**
  * Only allows requests whose learning path personalization query parameters ('forGroup' / 'assignmentNo' / 'classId')
@@ -15,10 +14,10 @@ export const onlyAllowPersonalizationForOwnGroup = authorize(
         const {forGroup, assignmentNo, classId} = req.params;
         if (auth.accountType === "student" && forGroup && assignmentNo && classId) {
             // TODO: groupNumber? 
-            // const group = await fetchGroup(Number(classId), Number(assignmentNo), )
+            // Const group = await fetchGroup(Number(classId), Number(assignmentNo), )
             return false;
-        } else {
+        } 
             return true;
-        }
+        
     }
 );
diff --git a/backend/src/middleware/auth/checks/question-checks.ts b/backend/src/middleware/auth/checks/question-checks.ts
index c83e1de2..38b1f0ef 100644
--- a/backend/src/middleware/auth/checks/question-checks.ts
+++ b/backend/src/middleware/auth/checks/question-checks.ts
@@ -25,7 +25,7 @@ export const onlyAllowAuthorRequest = authorize(
 
         const question = await fetchQuestion(questionId);
 
-        return question.author.username == auth.username;
+        return question.author.username === auth.username;
     }
 );
 
@@ -44,7 +44,7 @@ export const onlyAllowAuthorRequestAnswer = authorize(
         const sequenceNumber = Number(seqAnswer) || FALLBACK_SEQ_NUM;
         const answer = await fetchAnswer(questionId, sequenceNumber);
 
-        return answer.author.username == auth.username;
+        return answer.author.username === auth.username;
     }
 );
 
@@ -65,8 +65,8 @@ export const onlyAllowIfHasAccessToQuestion = authorize(
         if (auth.accountType === "teacher") {
             const cls = group.assignment.within; // TODO check if contains full objects
             return cls.teachers.map(mapToUsername).includes(auth.username);
-        } else { // user is student
+        }  // User is student
             return group.members.map(mapToUsername).includes(auth.username);
-        }
+        
     }
 );
diff --git a/backend/src/middleware/auth/checks/teacher-invitation-checks.ts b/backend/src/middleware/auth/checks/teacher-invitation-checks.ts
index 6ebc8512..27d0cab2 100644
--- a/backend/src/middleware/auth/checks/teacher-invitation-checks.ts
+++ b/backend/src/middleware/auth/checks/teacher-invitation-checks.ts
@@ -14,10 +14,10 @@ export const onlyAllowSender = authorize(
 
 export const onlyAllowSenderBody = authorize(
     (auth: AuthenticationInfo, req: AuthenticatedRequest) =>
-        req.body.sender === auth.username
+        (req.body as { sender: string }).sender === auth.username
 );
 
 export const onlyAllowReceiverBody = authorize(
     (auth: AuthenticationInfo, req: AuthenticatedRequest) =>
-        req.body.receiver === auth.username
+        (req.body as { receiver: string }).receiver === auth.username
 );
diff --git a/backend/src/routes/answers.ts b/backend/src/routes/answers.ts
index 2571c56d..a5ee6278 100644
--- a/backend/src/routes/answers.ts
+++ b/backend/src/routes/answers.ts
@@ -1,6 +1,6 @@
 import express from 'express';
 import { createAnswerHandler, deleteAnswerHandler, getAnswerHandler, getAllAnswersHandler, updateAnswerHandler } from '../controllers/answers.js';
-import {adminOnly, authenticatedOnly, teachersOnly} from "../middleware/auth/checks/auth-checks";
+import {adminOnly, teachersOnly} from "../middleware/auth/checks/auth-checks";
 import {
     onlyAllowAuthor,
     onlyAllowAuthorRequestAnswer,
diff --git a/backend/src/routes/questions.ts b/backend/src/routes/questions.ts
index 1363ae1a..bffcbe9e 100644
--- a/backend/src/routes/questions.ts
+++ b/backend/src/routes/questions.ts
@@ -1,7 +1,7 @@
 import express from 'express';
 import { createQuestionHandler, deleteQuestionHandler, getAllQuestionsHandler, getQuestionHandler } from '../controllers/questions.js';
 import answerRoutes from './answers.js';
-import {adminOnly, authenticatedOnly, studentsOnly} from "../middleware/auth/checks/auth-checks";
+import {adminOnly, studentsOnly} from "../middleware/auth/checks/auth-checks";
 import {updateAnswerHandler} from "../controllers/answers";
 import {
     onlyAllowAuthor,
diff --git a/backend/src/services/questions.ts b/backend/src/services/questions.ts
index 01e4cc5c..70400226 100644
--- a/backend/src/services/questions.ts
+++ b/backend/src/services/questions.ts
@@ -102,7 +102,7 @@ export async function createQuestion(loId: LearningObjectIdentifier, questionDat
     const question = await questionRepository.createQuestion({
         loId,
         author,
-        inGroup: group!,
+        inGroup: group,
         content,
     });
 
diff --git a/backend/src/services/students.ts b/backend/src/services/students.ts
index 95e836a0..09ba1643 100644
--- a/backend/src/services/students.ts
+++ b/backend/src/services/students.ts
@@ -59,7 +59,8 @@ export async function getStudent(username: string): Promise<StudentDTO> {
     return mapToStudentDTO(user);
 }
 
-export async function createStudent(userData: StudentDTO, allowUpdate = false): Promise<StudentDTO> {
+// TODO allowupdate parameter?
+export async function createStudent(userData: StudentDTO, _allowUpdate = false): Promise<StudentDTO> {
     const studentRepository = getStudentRepository();
 
     const newStudent = mapToStudent(userData);
diff --git a/backend/src/services/teachers.ts b/backend/src/services/teachers.ts
index 12148ebd..79072616 100644
--- a/backend/src/services/teachers.ts
+++ b/backend/src/services/teachers.ts
@@ -58,7 +58,8 @@ export async function getTeacher(username: string): Promise<TeacherDTO> {
     return mapToTeacherDTO(user);
 }
 
-export async function createTeacher(userData: TeacherDTO, update?: boolean): Promise<TeacherDTO> {
+// TODO update parameter
+export async function createTeacher(userData: TeacherDTO, _update?: boolean): Promise<TeacherDTO> {
     const teacherRepository: TeacherRepository = getTeacherRepository();
 
     const newTeacher = mapToTeacher(userData);
diff --git a/backend/tests/controllers/teachers.test.ts b/backend/tests/controllers/teachers.test.ts
index 39e59d6f..26a2d56c 100644
--- a/backend/tests/controllers/teachers.test.ts
+++ b/backend/tests/controllers/teachers.test.ts
@@ -15,7 +15,6 @@ import {
 import { BadRequestException } from '../../src/exceptions/bad-request-exception.js';
 import { EntityAlreadyExistsException } from '../../src/exceptions/entity-already-exists-exception.js';
 import { getStudentRequestsHandler } from '../../src/controllers/students.js';
-import { TeacherDTO } from '@dwengo-1/common/interfaces/teacher';
 import { getClassHandler } from '../../src/controllers/classes';
 
 describe('Teacher controllers', () => {
diff --git a/frontend/src/services/auth/auth-service.ts b/frontend/src/services/auth/auth-service.ts
index 7b0ff5ee..a813cd6e 100644
--- a/frontend/src/services/auth/auth-service.ts
+++ b/frontend/src/services/auth/auth-service.ts
@@ -29,10 +29,6 @@ const authState = reactive<AuthState>({
     activeRole: authStorage.getActiveRole() ?? null,
 });
 
-async function sendHello(): Promise<void> {
-    return apiClient.post("/auth/hello");
-}
-
 /**
  * Load the information about who is currently logged in from the IDP.
  */