How to restructure the array so is possible to store each answer and question_id in the answers table

If the user is doing a registration in a conference and selects quantity “1” for registration type general and “1” for registration type plus and click “Next” and goes to the registration form.

In the form, the user needs to introduce the name and surname for each participant this two fields are always mandatory for each participant being registered. Then, the registration type general has 3 custom questions associated with it, so for the registration type general the user also need to answer to that 3 custom questions. The questions and the answers answered by the user in the registration form were this:

Question                                  Answer
input text custom question                text answer
long text custom question:                long answer
checkbox custom question:                 check1answer

With the registration form below, and with the answers above, the participant array in the $request->all() shows like below. The name, surname, rtypes is stored properly but the answers and question_id are not be stored very properly in the array:

       "participant" => array:2 [▼
        1 => array:15 [▼
          "name" => "John"
          "surname" => "W"
          0 => array:1 [▼
            "answer" => "text answer"
          ]
          1 => array:1 [▼
            "question_id" => "1"
          ]
          2 => array:1 [▼
            "answer" => "long answer"
          ]
          3 => array:1 [▼
            "question_id" => "2"
          ]
          4 => array:1 [▼
            "answer" => "check1answer"
          ]
          5 => array:1 [▼
            "question_id" => "3"
          ]
          "rtypes" => "1"
        ]
        2 => array:3 [▼
          "name" => "Jake"
          "surname" => "K"
          "rtypes" => "4"
        ]
      ]

With the data stored like that using this foreach to insert the participants and the answers in the database shows "Undefined index: answer" in $participant['answer']:

foreach ($participants_list as $participant) {

    $name = $participant['name'];
    $surname = $participant['surname'];

    $participant_result = Participant::create([
         'name' => $name,
         'surname' => $surname,
         'registration_type_id' => $participant['rtypes']
    ]);

    Answer::create([
        'participant_id' => $participant_result->id,
        'answer' => $participant['answer'],
        'question_id' => $participant['question_id']
    ]);
}

Do you know to strucutre the array so solve the issue? So is possible to store correctly the answers of each participant in the answers table?

The $participant[0]['answer'] shows "text answer".
The $participant[1]['answer'] shows "undefined index answer".
The $participant[2]['answer'] shows "long answer".
The $participant[3]['answer'] shows "undefined index answer".