I freed 30GB using Filelight

In Germany "du hs" is considered an insult and I think that's beautiful.

du -sxk | sort -n gotta find those hidden files too!

This tool is amazing https://github.com/KSXGitHub/parallel-disk-usage

duf is pretty slick

If you need a more interactive method, gdu is awesome. And if you're using btrfs, btdu gives preliminary results instantly (which get more precise over time).