Hi just as a start might you go to Control Center / Disks and then click on your drive. Shown in my 1tb. drive of which the root 1 is using 26gb. of the 100 gb. I set it for. (Background had smaller drive set and using KiCad nightly builds was running out of space). My 2 is using 639gb. of the 900gb. and my 3 is 8mb. of 204mb boot/efi. List out your usage for your root, and home. Possibly remove unused programs. Some info here on various methods to free up space (not all inclusive). Might be able to remove swap as not needed in 22.04. Disclaimer not totally simple without further information.
edit forgot link and you have to click on each section. https://itsfoss.com/free-up-space-ubuntu-linux/
get rid of old kernels. If that does not make enough space you can use gparted to resize your partitions only by booting from a live usb. Remember, you cannot resize an active filesystem.
20gib is too small for a root partition, you should have at least 40gib. You can move and shrink/enlarge partitions having them unmounted, typically from a SystemRescueCD. Carefully! Make a backup of all you important files first.
thanks a lot. I used the commands and tips in the link and ran bleachbit.
After this I doubled my free space from 2,5 GB to 5 Gb. I think that should be enough for a while.
I also realized how much space snaps use. Maye I switch back to PPA with firefox for example.