If two effectively identical questions are asked but one in English and one in German, how do we handle these.
- Are they two completely different questions?
- Should one be closed as an exact duplicate?
Yes, it should definitely be closed as a duplicate. Leaving both open would only fragment the path to the correct answer between the two threads.
Remember that the closed, duplicate post will still be linked to the canonical answer-thread. It provides another way to find the content.
But there should only be ONE collection of answers to that question, not two. That's what "close as duplicate" is designed to avoid.
If I ask a question in English that has already been asked and answered in German I would not be able to understand the German answer and closing mine as a duplicate would mean that I would not receive the help I sought.
I mean there is incentive for answering my English question, since you'll get rep if your answer is accepted and/or upvoted. There is very little incentive for translating the German question. Also there might be relevant comments and translating all comments too doesn't seem feasible.
So in my opinion you shouldn't close the English question as duplicate unless the German question provides translations of all posts and vice versa.
I would not be against having one English and one German version of each question and have them linked to each other, rather than closing one of them.