Hello Nico-Gumby and moxiejeff and a happy new year to all. Many thanks for your answers. I have now been able to fix the problem and everything is working as it should. I hate to say it, but the cause of the problem was once again sitting in front of the screen. After I had assigned the correct throttle axes in the MSFS control options and calibrated the throttle again in the EFB, everything was ok. Now starting to learn and to enjoy this bird.
Thanks, Norbert