> Now, if I try to update, it says: " The following > signatures couldn't be verified because the public key is not > available: NO_PUBKEY B4EFB9F38D8AEBF1". :((
That is the trisquel archive signature, you may have removed it somehow. You can put it back with this command: wget -o /dev/null -O - \ http://archive.trisquel.info/trisquel/trisquel-archive-signkey.gpg |\ sudo apt-key add -
