For a situation like this, my two favorite tools (which I think probably are preinstalled by default) would be:
- gnome-disks, to see the capacity of your storage drive and to see how your partitions were laid out
- baobab (a.k.a. “Disk usage analyzer” or something like that), to analyze your /home partition (or “/” even) and figure out graphically what consumes the most disk space. It’s a life saver.