Someone stole my account gog please advice

Ask GOG support for help?

Contact GOG support, be honest with them and don't try to hide anything from them. Even if you bought it from some shady website.

Ask GOG support for help.

Contact GoG support and sort it out. Proof of purchase, card number and stuff like that will probably be needed. Also Boxed version of Witcher 3 ? I'm pretty sure they didn't have GoG codes in them O_o.

GOG support for help ask?

I bought witcher 3 in shop (tesco) and boxed version have a key.I will send them a mial with c-d key gog and name account <like a steam when hijack account> I hope gog feedback me ;_;

Not sure if suggested, but contact support of site where you lost your account. That will be GOG no?

Gog security supposedly is very tight so doubful someone just found/hacked your account. Seems you either used a very simple password or you got some very poor security/you clicked some phishing link.
Still the whole story seems a bit strange, and this is not gog support.

The couple of times I've contacted GOG support they have been extremely quick with their reply and very helpful. Their Support is as quality as their games; which is to say 10/10. :)

Hi,

Can you please explain further what happend? With this information I don't have any information. Could you place take a picture with the witcher box and the text ''Steamgifts isn't GOG.''. Any extra information would be helpful, for example where did you buy the game? Here is a Support page. If you've any other questions please email us.

Greetings,

Not a GOG member,

Drafek

Contact GOG support, tell what happened and give them all the necessary info like past email id, proof of purchases, cd keys of activated games, etc. I'm sure they'll sort out the issue soon

GOG support might be able to help you