Ok, finally I got the serial controller ONLINE after changing the Port from AMA0 to ACM0. For that, I replaced
-Dgnu.io.rxtx.SerialPorts=[...]/dev/ttyACM0:/dev/AMA0
with
-Dgnu.io.rxtx.SerialPorts=/dev/ttyACM0
(got that idea while reading
fixed the permissions as suggested in
But now, I still cannot get the smoke detector connected. How can I now start the inclusion mode of the UZB stick? Do I see that with some light flashing?
What I tried was to search for things in Inbox and than pressed the button on the smoke detector three times, but no success.
Trying to add a thing manually brings me back to add a serial controller.
Sorry, seems I’m a little bit blinded at the moment.
Thanks so far to everyone helping me to get the serial controller online. 
Regards,
Carsten