Verifications payment & training

When I add a payment for a student in my form payment

the student can have 2 trainings (so, 1 payment = 2 trainings)

When, I want to add a second training in my form training, it blocks

In my Controller Training I have this:

public function store(Request $request)
    {
        $request->validate([
                'date_seance' => 'required',
                'hour_start' => 'required',
                'hour_end' => 'required',
                'fk_motorbike' => 'required',
                'fk_former' => 'required',
                'fk_student' => 'required',
                'fk_typeseance' => 'required'
                
                
        ]);


       $date_seance = $request->get('date_seance'); 
       $hour_start = $request->get('hour_start'); 
       $hour_end = $request->get('hour_end'); 
       $fk_motorbike = $request->get('fk_motorbike');
       $fk_student = $request->get('fk_student');
       $fk_former = $request->get('fk_former');
       $fk_typeseance = $request->get('fk_typeseance');


       $payments = Payment::where('fk_student', $request->get('fk_student'))->first();


        if(!isset($payments)){ 
            return redirect()->route('trainings.index')
                    ->with('error', 'No payment, no training! ');
        }
       
        $thisStudentsTrainings = Training::where('fk_student', $fk_student)->get();

        if(count($thisStudentsTrainings) >= 2){ 
            return redirect()->route('trainings.index')
                ->with('error', 'The ceiling is 2 trainings! ');
        }

        $thisStudentsPayments = Payment::where('fk_student', $request->get('fk_student'))->get();


        if( count($thisStudentsPayments) < (count($thisStudentsTrainings) * 2) ) { 
            return redirect()->route('trainings.index') 
                ->with('error', 'test!'); 
          }


        else{
            Training::create($request->all());
                return redirect()->route('trainings.index')
                    ->with('success', 'Add');
        }

       

    }

I think the problem is here ?

if( count($thisStudentsPayments) < (count($thisStudentsTrainings) * 2) ) { 
            return redirect()->route('trainings.index') 
                ->with('error', 'test!'); 
          }

Thank you for your help.