> I have absolutely no idea how anyone could make a fun game that revolves around German grammar.
WWII is a pretty common setting for games. Making the German protagonists communicating only in German would be a first step to incentive learning the language.
Have an English language game where enemies talk in German, where being able to understand them gives you an advantage, for example because you know what they're about to do.
Then mix and match for different languages.
Of course the things they say should be more detailed and diverse than just some standard sound clips.
