Is there a way to change a game language without changing the entire system language ?

Make sure the game supports language swapping, some support this feature.

It depends on the game, it will be in settings if so, I use to change battlefield language to something else when family are around because the cursing.

The only option it's that the game have a menu to change the language.

Games from Ubisoft have that menu, but games from Microsoft don't.

Regards!

depends on the game, some have this fun, others do not.

If the game you're playing is supported in another language or multiple languages then, in the settings/options of whatever game it is there should be an option to change the voice and dialouge languages. Its most likely gonna be under audio/sound. If you
don't have that option then the game isn't support for any language outside of English or if the option is there and you can't find the one you want you may only have a small selection of languages that the title is supported in.

Language support is avaliable at the discretion of the developer/publisher. You may wanna check online to see what languages its avaliable in before buying or downloading next time.