Somebody can tell me where can i find my activation key in gog galaxy after activation?

I do not use Galaxy, but I do know another way if you may be interested.

In your browser, go to your account page. Games. Choose the game in question. Click the More toggle menu on the right side of the game chosen. Should be a listing for Serial or activation code if required at all.

Hope that helps.

What the heck would you need an activation key for?

Steam?! O.o

That's actually the only way. It's not possible to look up serial keys in GOG Galaxy, only via web browser.

Two Worlds - Multiplayer key - GOG Support Center has an animated image explaining the above. It's the same for any game that has a serial number, whether it's for multiplayer or a second copy to gift to a friend.

*looks at profile* One game, but two games played mentioned.

First guess: You're going to contact support regarding a missing game and you want the original GOG key as proof.
Second guess: You bought that key on one of those greymarket key-reseller sites.
Third guess: It's Cyberpunk which is missing.

*sigh* You kept your email when you redeemed your key, right? You kept your receipt & CC details when you bought it either from GOG directly or one of its very few official reseller stores?

The more ya know...thanks for the info mage :)