RSS Title Doubled!

Have you ever seen anything like this?

In WordPress everywhere is set the correct name and url of m website (mobiwatch.de).

But since some days the title of the rss feed (http://mobiwatch.de/feed/) shows a doubled title: “mobiwatch.demobiwatch.de | ” (yes, that pipe” sign at the end is standin there, too).

I don’t have a clou how this happened and how to fix it.
Has somebpdy any idea how I can change that?

Please note that I’m no pro at all, so if you can supporthelp, please name files and/or codes in full length, because I couldn’t find/use them otherwise ;))

Thanks in advance!!!!