ITNinja

You may most certianly post in German, or any other language. We have some longer term plans to offer localized instances of the site but it will be some time before that will be available. 

That said, it is not common for people to post in other languages so I'm not sure how severly doing so will affect the quality or quantity of responses. But, I say go for it! If you don't get a good response, you can always edit the post later and paste in a translation from something like Google or Bing Translate. 

If you write it in English then you can cover more audience.

Your English is very good