What to do with fg after quit game??
Can be turn into paypal back???
Or is lost???

The Fg stays on your account till you decide to use it. If you're quitting your current game, there are several other games you can use your Fg for. So, to answer it simply it is not lost.

You CANNOT sale your Fg.



Taken from here;
https://forums.d2jsp.org/info.php?p=9

FG can be used for trading in orher games, services such as graphics, etc. But all purchases are final. There are no reimbursement or conversion back to monetary value.

You can use fg to buy items from other games. I suggest osrs gold, what you decide to do with that gold after buying it vs fg has nothing to do with d2jsp

You can donate all of it vs star upgrade.

You can buy certain currencies and in turn trade them for money.
Just a loophole most people do to cash their FG out legally.

might take a look into this subforum:
https://forums.d2jsp.org/forum.php?f=279