The “No space left on device” is a pretty good clue to what the something is.
Did you try the commands the CLI listed as what you should do?
You don’t need to be afraid, you need to be extremely careful.
For those familiar only with GUIs, CLIs can be intimidating.
But they are what computers used to be way back before there was HTML
Just type very carefully and double check before you hit enter.
Usually a typo won’t result in a catastrophe, but that depends on what the typo is.
If you missed my saying it - be careful