To fix that, you can reinstall Trisquel and you do not need to backup (or transfer the data from your DVDs) again. An XFS cannot be shrunk but it can be extended. That is why you can remove the root partition from the Live system and extend the home partition (running 'gparted'). Then you can proceed to the reinstall choosing a custom partitioning with the correct home partition but without reformating it (a case to check). The root partition would be created in the remaining free space. You can either create this partition from GParted or from the installer.
You made a 198 GB root partition?! This is far to much. 16 GB should already
be more than necessary. You will soon run out of space on the home partition.
On the contrary, I do not even think that you can fill a 198 GB root
partition. Installing everything in Trisquel's repository may not even take
that much space.
