There are flags which could be chosen when creating a topic.
I know that there is a bunch of more or less important stuff also discussed in these topics but most of the time very specific to a question where the creator maybe cannot express himself in english to make clear what he means.
I for myself try to choose the english language when creating topics which could also be in general interest. But when someone opens a topic in german, why should i respond in english? Maybe they have to look up everything in the translator, too when reading the english posts?