As it turned out, all the actions that I advised you were not needed. My apologies.
The settings you made initially are enough. The error occurred because the nautilus-share extension is deprecated. There is no error when creating shares from the command line.
For example (without sudo):
net usershare add Documents /home/fp/Documents '' '' guest_ok=y
Optionally, you can remove unnecessary:
sudo groupdel sambashare
sudo rm -r /var/lib/samba/usershares
sudo rm /etc/samba/smb.conf
