Drupal 8.x

My form works well with the main theme, but in seven (admin theme)  I get this error :
 

Deprecated: call_user_func_array() expects parameter 1 to be a valid callback, non-static method Drupal\mais\Form\annuaireForm::usernameValidateCallback() should not be called statically in /home/almedest/public_html/dev/mais/core/lib/Drupal/Core/Form/FormAjaxResponseBuilder.php on line 69

I wonder if it's a callback reason (used of addCommand) or the call of the callback

callback :

Hi there

I have an error message in German "Nicht übereinstimmende Entitäts- und/oder Felddefinitionen." roughly translated as there being inconsistent entity and/or field definitions and that I should Uninstall "node.field_media_gallery_image" ...

How/where do I do that? I originally had the image gallery module installed, but since it could not do what I wanted as it has less features than the D7 version, I uninstalled it and have long since got another, but get this error under status report.

I would appreciate your help.

Hello all,

I'm performing security updates on a few Drupal websites, one of them uses the Acquia Lightning Distribution (https://www.drupal.org/project/lightning), I'm trying to update this distribution from version 3.1.05 to the latest version (3.2.7).

Hi,

I have created a module and create entity inside which call 'annuaire'
here are my files created for the entity :
annuaire.php
annuaireForm.php

in annuaire.php I define a field :

Hi,

I have recently started working with Drupal but I have an issue while accessing "Install new module" from the Drupal interface to install modules. It shows Forbidden: Access is denied; the same is with "Update".

Drupal installation is not new, it has been developed by someone else and now not sure why is it so.

Any ideas?

Thanks