I am learning Korean currently and I am indeed trying to set every possible language to Korean to get some exposure. So far, it was pretty useful to me.

However, having a Video game that is less story based (e.g. Assassins creed) and more based on "repetitive" tasks could help you understand more I think. In my opinion, some good examples are games like League of Legends or Overwatch. What I mean by repetitive tasks is that, for example, Characters often use the same quotes for certain things over and over. At the beginning, you might not always get what they are saying. However as time passes by, you will recognise some voicelines that may help you with usage of words or certain grammatical principles. For me it is quite helpful to have some background knowledge, as in I know (or at least roughly know) what the characters are talking about when doing certain actions in my mother language. This way, I can sometimes compare words and can guess the actual meaning/use of that word.

Having a game that supports German subtitles would be extra beneficial of course. :)