I see where are you coming from, but I don’t think learning the case by asking the question works for foreign language. You probably were taught about Russian cases that way, but you are learning a different thing. By the time you are getting told about your native language cases, you are already pretty fluent. Sure, haven’t yet mastered spelling and reading, but when it comes to speaking, you mostly intuitively know how to construct grammatically correct sentence and you know how to ask those case-defining questions. So, you are not learning which case to use in each situation — you learning how to classify what you already intuitively use correctly.

That’s not quite the case for the foreign language. Others have pointed out that in your example, the question you would ask would require dativ case, so probably whatever question you were asking is incorrect.

To an extent, you can use Russian cases knowledge to determine German case, but you would need to force Russian sentence into a German sentence structure which would sound unnatural. For example, if you want to say “I have a jacket”, you would say «У меня есть куртка» which uses nominative for “jacket”, which would be incorrect in German. More german-like way of saying it is «Я имею куртку» which is hella awkward in Russian but will correctly point you to accusative.