fileupload getting null

Im getting an error when I try to upload a file:

Call to a member function getSize() on null

    public function uploadAssesment(Request $request, Course $course)
    {
        $file = $request->bestand;
    }

 <form action="/upload/assesment/{{$course->id}}" method="POST" enctype="multipart/form-data">
                        @csrf
                        <input type="hidden" name="id" value="{{$test->id}}">
                        <input type="file" name="bestand">
                        <input type="submit">
 </form>