Hi, i use Steam and if you know here Are community market And item trading, i want know if Are Steam only one where is or some more services or games where Are poosible to trade my items? I know Is Offtopic, but i need reply. Thanks you.

There is currently no community market or item trading system in place on gog. Sorry!

Okay, but you know if some service where trading like Steam?

Steam trading is its own self-contained thing. There are many 3rd party sites that do trading with steam items, but I definitely would not recommend any of them- they're probably all far too easy to abuse and scam people through.

But if you're looking for trading cards, let me help you start your collection with a limited edition gog game card!

No i dont want sites fór Steam trading, i asking if some service like Steam have trading in their system. Or if Steam only one where poosible to trade my items

Try Magog.

Magog doesn't have any trading in its system. Nor do any of the other game services, honestly- at least nothing beyond glorified game gifting system.

There are no such services for GOG games etc. official nor unofficial. People trade games in the forums here though, one just has to read the initial posts in them to learn the rules, and establish some reputation (not rep score, but actual reputation via participation) in the forums in order to earn trust in the individual's eyes. Some people may use Steamrep or other mechanisms to help determine who to trade with.

Other than that, there isn't any other trading mechanisms that I'm aware of with respect to GOG stuff.