Ok, once again: thank you BRENT for your detailed help and your hint to the sequence of events!!!
I removed AUDACITY with:
sudo eopkg remove --purge audacity
On terminal it needed quite a few seconds (10-20) when it automatically worked on:
updating clr-boot-manager
updating mimetype database
So i can only guess that AUDACITY is changing these 2 fundamentally, when its being installed.
Finally automatically updating the "icon theme cache", "desktop database" and "manpages database" did not take that long.
Then i did another:
sudo update-grub
Finally another:
sudo eopkg check
Drove down the system. Booted again 2-3 times. Booting time back to 1 MINUTE !!!
So from my experience, installing and starting AUDACITY changed my "usual" 1 Minute-booting-time to 2.30 Minutes.
I hope this helps if someone meets the same problems.
