mate does not fully follow the French language in the Belgian region

hi !!
I'm writing to you today for a little localization bug, with French(Belgian), ubuntu mate ends up with some apps in English (vokoscreen, ubuntu-mate-welcome, software-boutique, menu is translated 98% french but 2% english, and a lot of other errors like that, while the French(French) version works perfectly and doesn't have any translation errors, at least not the ones I'm quoting about

https://imgur.com/a/Yymuy9u

I don't think it should be complicated to solve, it should just take the full French translation, I don't really understand what's going on under the hood

thank you for reading and we look forward to helping you in the future