Problem: If you up/downgrade a Debian most of unneeded files are always on your disk
Solution:
To check:
$sudo dpkg -l | more
To cleanup:
dpkg --list |grep "^rc" | cut -d " " -f 3 | xargs sudo dpkg --purge
If you like run the command twice cause sometimes deps are new taken
or install deporphan to:
$sudo deborphan | xargs sudo apt-get -y remove --purge
If you like run the command twice cause sometimes deps are new taken