Here is what you need to do to see what is on /dev/loop0.
sudo mkdir /mnt/loop0
sudo mount /dev/loop0 /mnt/loop0
cd /mnt/loop0
ls -la
This will allow you to move the files to an alternate location off the machine and once the files are moved I would delete the devices since you have the data if it is necessary to still remove the devices due to growing storage.
I would suggest that you do something along the lines of sudo nautilus
then do a select all copy and paste the files on to an alternate location like google drive or a location with a large storage area that can grow. Because those loop files can have a large size once extracted themselves.
An additional note a /dev/loop with a assigned number is a block device for an snap application. Your /dev/loop0 is full because you continue to use the app associcated with the block device and whatever that app is creates or increases the block device sized based on usage if it is full then you need to uninstall the app or move the app install location to a different drive.
Here is the way to tell what application is using the /dev/loop0 and filling your drive space.
Execute in a administrative shell the following command.
losetup
It should output an example as such.
NAME SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE
/dev/loop0 0 0 1 1 /var/lib/snapd/snaps/bare_5.snap
So clearly we know now that the bare_5.snap application and processes on the block device have filled its allotted size limit.
For further explination on block device management and how file systems compress please reference the following link.
system mounts /dev/loop0 on /snap/core/3604 and it's 100% full, where is it coming from?