处理大的symfony形式

I'm having some nested collection type in my symfony project.

Etablissement > Classes (5 per etablissement) > Matieres (15 per classe) > Ressources (X per matieres, the user can only create ressources)

This is giving me a performance problem, because my php memory limit is almost reached, an sometime the website is crashing !

More, the SF cache is almost 18Go for only one form !

Perhaps I'm doing this the wrong way, but I don't know how else to do.

When I doing rendering my form, I'm forced to render ALL form field of ALL, even the one not needed.

I'm doing this to hide them :

            <div class="row d-none">
            <div class="col">
                <input type="hidden" name="user_id" value="{{ user.id }}" title="user_id">
                <input type="hidden" name="etablissement_id" value="{{ etablissement.id }}" title="user_id">
                {{ form_widget(form.code_etablissement) }}
                {{ form_widget(form.type1) }}
                {{ form_widget(form.nom) }}
                {{ form_widget(form.type2) }}
                {{ form_widget(form.email) }}
                {{ form_widget(form.ville) }}
                {{ form_widget(form.lycee) }}
                {{ form_widget(form.code_postal) }}
                {{ form_widget(form.adresse) }}
            </div>
        </div>

VERY WRONG I know, but without it, the form can't be submitted.

Example of errror :

Expected argument of type "string", "NULL" given at property path "code_etablissement".

And to display my form, I need to loop over the form fields.

Ex :

    {{ form_start(form) }} //etablissement
{% for classe in form.classe %}
                            <div class="d-none">
                                {{ form_widget(classe.nom) }}
                                {{ form_widget(classe.specialite) }}
                                {{ form_widget(classe.serie) }}
                            </div>

{% for matiere in form.classe %}
 ... etc
{% enfor %}
{% enfor %}

I really need your help !