How to use CollectionType class on Symfony?

I made a form with Symfony. I am using CollectionType class in order to send several information from one input that I can duplicate. (see my code below)

The field is missing. I didn't succeed to get a select and choose the language I wanted. Instead I have all code in data-prototype which is unexpected. (see the picture at the bottom)

So here is what I did :

registration.html.twig

{% extends 'base.html.twig' %}

{% block main %}

{{ form_start(userform) }}

        {{ form_row(userform.wishedlanguages) }}

        <button type="button" id="addwishedlanguage">+ Add language</button>
        <button type="button"id="removewishedlanguage">- Delete language </button>

        {{ form_row(userform.save }}

{{ form_end(userform) }}

{% endblock %}

UserType.php

<?php

namespace App\Form;

use App\Entity\User;
use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolver;
use Symfony\Component\Form\Extension\Core\Type\SubmitType;
use Symfony\Component\Form\Extension\Core\Type\LanguageType;
use Symfony\Component\Form\Extension\Core\Type\CollectionType;

class UserType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options): void
    {
        $builder
            ->add('wishedlanguages', CollectionType::class, [
                'entry_type' => LanguageType::class,
                'allow_add' => true,
                'allow_delete' => true,
                'prototype' => true,
                'label' => 'Quelle langue souhaites-tu pratiquer ?',
            ])
            ->add('save', SubmitType::class, [
                'label' => 'Je valide',
            ])
            ;
        ;
    }

    public function configureOptions(OptionsResolver $resolver): void
    {
        $resolver->setDefaults([
            'data_class' => User::class,
            'translation_domain' => 'forms'
        ]);
    }
}

Here is the code I can see in the browser :