Module development and code questions

Hello,

 Im using commerce installments 

Hey !

I'm starting to develop on Drupal and I don't really understand how events work.

I have a content called "dossier de soutenance".

My goal is to create a module that fills in a "dossier de soutenance" field when one is created. 

For the first one, the field must have the value 0, then the second the value 1, then the third the value 2. Then we start again at 1, so the 4th will have the value 1, the 30th will have the value 0...

RuntimeException: Failed to start the session because headers have already been sent by "/var/www/html/vendor/symfony/http-foundation/Response.php" at line 1239. in Symfony\Component\HttpFoundation\Session\Storage\NativeSessionStorage->start() (line 152 of /var/www/html/vendor/symfony/http-foundation/Session/Storage/NativeSessionStorage.php)

This is the code that causes it:

Hi, in a views I have inserted a filter on a date field.
I checked that everything was working fine with change of date and more.
The next step is to assign a default date.
Through form_alter and in particular in id $form_id == 'views_exposed_form', I value the data filter through this parameter
'#value' => '2022-01-03' and it works.
The problem is that when I change the date, it always returns the date I indicated in the code and not the chosen one

I tried with '#default_value' => '2022-01-03', but it just doesn't display the date

I recently changed my site. But now the background area has suddenly started showing bluish color which I never intended. Could anyone please let me know how I could change the background color of the main body area to white? The address of the site is as follows.

https://www.japaneseautoworld.com/

Thanks and regards