@norder The change to T100000 made the difference - but I have put 84000 there wich is the resistance I measured at around 18°C and that made no difference.
And no I did NOT just copy someone else's config.g . I just saw the line in the config.g and gave it a try . I will definetly do a PID tuning for both - because I need to do this twice a year due to the fact that the temperatures of winter and summer are quite different in Austria.
Thank you for your effort!