if i make a topic and someone wants to buy my item, how do i give this item???
Do i have to sell it on the market for 1 fg???

you can sell it for more than one
generally say you're selling me an item and I bid 250 on it, you'd put it on the marketplace for 250 and I'm in agreeance that I'll go buy it for 250
sometimes it happens that people won't buy it and you've had to waste fg on the marketplace fee
but if we agreed to 250 and you put it up for 1 and expect me to send you 249 after, that's called dodging the marketplace fee and it's a lockable offense

t4i
that helped me alot=)