Assign value to a Model's table

Hello,

I have 2 Models: User with the attribute of type string type

Schema::create('users', function (Blueprint $table) {
            $table->increments('id');
            $table->string('first_name');
            $table->string('last_name');
            $table->string('email')->unique();
            $table->string('password');            
            $table->integer('enrolled_courses')->unsigned()->nullable();
            $table->integer('course_id')->unsigned()->nullable();
            $table->string('type');
            $table->rememberToken();
            $table->timestamps();
        });

Schema for model Course:

Schema::create('courses', function (Blueprint $table) {
            $table->increments('id');
            $table->string('name');
            $table->integer('student_id')->unsigned()->nullable();
            $table->integer('tutor_id')->unsigned()->nullable();
            $table->dateTime('date_begin');
            $table->dateTime('date_end');
            $table->string('spoken_language');
            $table->text('description');
            $table->timestamps();
        });

I want to be able to distinguish between Student and Tutor with the attribute type

I am getting the Tutors and Students with the following method:

public function index()
    {

        $tutors = User::get()->where('type', 'tutor');

        $students = User::get()->where('type', 'student');

        return view('course.create.index', compact(['tutors', 'students']));
    }

with a foreach loop I am rendering them with their Ids.

Relationships between the models Model User

public function courses()
    {
        return $this->hasMany(Course::class);
    }

Model Course

   public function students()
    {
        return $this->belongsTo(User::class)->where('type', 'student');
    }

    public function tutors()
    {
        return $this->belongsTo(User::class)->where('type', 'tutor');
    }

There is an admin who create Courses with the following method:

public function store(AdminCreateNewCourseRequest $request)
    {
        $this->authorize('create-course');

        $course = new Course;

        $course->name               = $request->name;
        $course->tutor_id           = $request->tutor_id;
        $course->student_id              = $request->student_id;
        $course->description            = $request->description;

        $course->save();

        $user = User::where('id', $request['student_id']);
        $user->course_id = $course->id;

        return redirect($course->path())
            ->with('flash', 'The course has been published');
    }

I am trying to assign the Id of the course to the student or tutor.

It doesn't work and my relationships are not working as well

I am sorry for the long explanation

Thanks