We allow English only in public chat or public posts, but in pm's you can use any language. Unless you are unable to speak English and trying to get help we can translate it. Here is the quote right out of the rules
To add on this...if you need help or support we do allow german if you can't communicate your issue in English, however just be aware that it may take some additional time to get to your request as only a few people speak it. We want to make sure you get the help you need to keep playing =)
