found out already, that it might be KABEL...

Sorry, but I don't think so. At least the Kabel I have has rounder tops of the a, diamond umlauts and k doesn't touch the ground straight.

My typografical vocabulary is not quite correct, but see for yourself:

Unfortunately I don't know what it is.

It is Kabel, albeit not the ITC version, but the proper one by Rudolf Koch, made by Stempel and available from Linotype via

http://www.fontshop.com

My apologies, I didn't know there were two Kabels, and that I had the not proper one.
How embarrasing....