Welcome to the forum!
Maybe Moini will reply for you in German, if that would be helpful.
because it get always bended with the bottom on the circle!!
It's supposed to get bended with the circle. Do I understand correctly that you don't want the text in a true circle, but more of a flattened circle?
If you don't hold Ctrl key while you draw the circle, it will draw an ellipse, which is a flattened circle - like below. Is that what you want? I had to add some spaces in front of the text, to make it look centered.
Edit
Oops, and I also had to flip the circle and text horizontal. For some reason, Inkscape is putting the text upsidedown and backwards. I don't know if that's a new bug, but I don't remember it doing that before (although I haven't used text on path for quite a while, so I couldn't say which version where it changed).
As I recall, it used to always start the text at the left handle or node, and proceed to the right and over the top of the ellipse. But now, it's starting at the right handle/node and proceeding upsidedown and backwards under the bottom of the circle.
