My problem is somewhat similar to http://meta.mathoverflow.net/q/1862/99468. But in my case the question has not been answered at all. My first idea was to write a comment below the question. But you need 50 reputation for that and I just created this MO-account. So one option would be to wait till I get enough reputation, but that can take a while. Another option is to create a new question and link it with the old one. And the last option is not to ask at all. The question I want to ask has been asked here: http://mathoverflow.net/q/233870/99468. It is really detailed and contains everything I want to know. So the best thing for me would be to "activate" this old quesion. Is there any way to do this?