I speak a bit of German and it is indeed a very strange e-mail. Not written in German by a native German speaker (Or maybe a not very well educated one). It says both - "we will not answer you anymore" and the equivalent of "please contact us if you have any more questions". And indeed, it ends with "best regards".

But there seems to be more to the story. Notice that the e-mail is in response to an e-mail from the day before - responses this quick are virtually unheard of these days. And from the tone I have a hunch that there were other e-mails exchanged before this one.