The permissions to create and edit in category "Informatique et SIG" for user group "fiche_pratique_DSI_agents" are set to "inherit". They should inherit from the parent category "Mon service" and therefore should be "not allowed".
Maybe something with your #__assets table is wrong.
Before you do anything else, make a backup of your database.
Then I would try to change the value in column "rules" for category "Informatique et SIG" in table #_assets from {"core.create":{"9":1,"83":1} ... to {} (same value as for category "Mon service") and see if that works. If nothing happened or something went wrong --> revert to backup.
If it did not help you could install an extension, for example ACL-Manager. It will show you if there are any problems with your ACL and fix them for you.