Welcome to Trisquel Misty!
I have a similar situation to you with an old mini-laptop (full description
here: https://trisquel.info/en/users/strypey). I was running full Trisquel 7,
and with help from some of the folks here, I identified that the issues I was
having were to do with insufficient RAM. As mentioned above, I started using
Enlightenment instead of GNOME Shell, which works a lot better but still had
some issues. So, I installed Trisquel-Mini in a separate partition to see if
it works any better (not really).
What I suggest you do is back up any files you want to keep (your documents,
photos etc) onto USB drives (*), and start again from scratch.
1) Delete all existing partitions, and create new partitions, using GParted,
from a live disk (eg a Trisquel install disk or a GParted-Live disk:
Everyone has their preferred partition scheme, but I suggest something like:
* 20GB ext4 main OS partition: this is for the OS you are using on a daily
basis. 20GB is large, but that gives you plenty of space for future updates,
installing more applications and games etc. 10 years ago 5B was more than big
enough, so making it 20GB should be future proof for at least that long, and
you'll be lucky if an ex-Windows computer is still usable in 10 years, even
running GNU+Linux and lightweight desktops.
* 10GB ext4 test OS partition: this is for when you want to test other
GNU+Linux distros or versions
* ext4 /home partition: this takes up whatever space is left on the hard
drive, and is for your documents, photos, music, videos etc.
When you install a new OS to your main OS or test OS partition, you can mount
this partition as /home. Then all your files will be available under 'Home'
when you boot the new OS, and any files you create will be stored there and
accessible from any other OS you set up this way. Make sure you *DON'T* tick
the 'format' tick box when you do this!
As an example, my mini-laptop currently has 3 partitions:
1) Full Trisquel 7 (GNOME Shell) plus Enlightenment (or OpenBox for games)
that has been my primary OS
2) Trisquel-Mini 7 (LXDE) plus Enlightenment that I've been testing
3) Separate user files partition, mounted as /home
Once you have a partition scheme like this set up, it becomes much easier to
test drive other distros or versions without interfering with your day-to-day
OS or repartitioning. It also makes it easier to reinstall your main OS
without having to copy all your user files off the computer and back on
again. It's always a good idea to make sure you have recent backups,
especially when you are installing a new OS, but unless something goes wrong,
you won't need to use them. Again, this is only true if you make sure you
*DON'T* tick the 'format' tick box when you do this! The potential to make
mistakes like this is why it's worth making sure you have fresh backups
before you get started on any new install.
* Storage tip: you can get 256GB USB drives from about $50 now. Four of those
gives you about 1TB of storage for about $200. You can get a a 1TB USB
magnetic drive for much less than that, but USB flash drives are much less
likely to crap out. If you have your data spread across a collection of
smaller flash drives, you're spreading your risk, and it's a much less
appealing target for thieves than a 1TB magnetic USB drive.