Ubuntu: snap remove firefox permission denied [Solved]

In my case, I could not remove firefox on Ubuntu 22.04. The command sudo snap remove --purge firefox did not worked. I had this error:

error: cannot perform the following tasks: Remove data for snap “firefox” (XXXXX) (unlinkat /var/snap/firefox/common/host-hunspell/xx_XX.dic: read-only file system)

I tried to reinstall also snap, but the error did not go away.

So that I unmounted host-huspell:

sudo umount /var/snap/firefox/common/host-hunspell

and I finally was able to remove the snap firefox.