Dunno which is your ext4 partition. Maybe i should remember that from reading a previous post.
Anyway, one thing to look at is how many kernel images are on your system. And along with them all the headers and suchlike that come along with them. There’s an apt command that’ll do that but i’ve never done it. Another thing you can do is have apt clean up its cache where it stores the .deb files it’s downloaded.
What i’d start with is running Baobab to see where the space is. In the main menu it’s under “System Tools” as “MATE Disk Usage Analyzer”. If you haven’t used it before, it’s quite good imo. However if you have a bunch of links, especially bind links as i’m prone to use, it can get a little confused about which filesystem is being talked about. In any case i’d start there since its pie-charts will let you home right in on the fat places, then you can decide what tools are best for cleaning things up.
Assuming that your ext4 partition immediately follows your root partition on the device, to expand the root partition you’d have to resize or move the ext4 partition and then resize the root partition.
I’d start with The “MATE Disk Usage Analyzer” myself. HTH.
