Did you read the link I pointed you to ?
Lets look at the smb.conf you are using now:
You don't really need the workgroup line, it is the default.
You do not need both 'Security = user' and 'server role = standalone server'
Now for the share:
'available = yes' and 'browsable = yes' are defaults, so are not needed.
'only guests' is actually 'only guest' and the default is 'no', so again not needed
'public = yes' and 'guest ok = yes' mean the same thing, so you only need one, but you haven't set 'map to guest = bad user' in global, so whichever you pick will do nothing.
Read our documentation: https://wiki.samba.org/index.php/Settin ... one_Server