Speak in English if you want players from all over the world and not only Germans. None likes see a server speak only one lang.Speak only in english when you write something(Why do i say this?Because all knows speak english today,and when you speak in german you just penalize the players from the other countries),then you will see the big difference..Trust me,you will thank me.
Many players can quit from the server when they see the players speak only one lang, because is really boring get full chat writed of a lang that you don't know!
I don't mean none can speak in german,but at least the admins/gms must speak only in english for let all know what does they say, and this may please many players too
Take it just like a suggestion