Module installed manually not shown

[danger-m]

Hello,

I'm trying to add custom fields to the categories in my shop under PS 1.7.8.10 (freshly installed version). According to the documentation, you need to create a custom module for this. I've tried creating a module folder and the class that goes with it, but it doesn't appear in the list of modules or in the marketplace menu, but it does appear when I search with the name via the search bar, and when I click on the name of my module, it just redirects to the marketplace page without error. I've tried using an example code, but it doesn't work either. i also make test with this example : https://github.com/PrestaShop/example-modules/tree/master/demoextendsymfonyform3

Thank you for your help