i don't know how to activet a cd key on GOG can you help me ?

Well you can redeem GOG codes here.
And there are about a handful of games you can redeem by using their CD code/product code which you can find here.
It would help to mention what game you're talking about and where said code came from.

here >> https://www.gog.com/redeem

... Well, purely for educational purposes of course, you put an accent where you were supposed to put an apostrophe.

Always funny when people are oblivious of their own mistakes while being right in the middle of correcting others ...

Well, in the english language the accent is used this way. And also in modern german internet german it`s normal to use the accent instead of the catastrophe! :-))

It's even worse than I thought ...

Please stop trying to correct others, or justify mistakes. Friendly suggestion.

Also, I'm sure you are aware of the correct spelling of "English" and "German" when referring to the languages ...

Really, if the meaning is conveyed, why do you even bother?

Well, I`m not perfect, of course. And yes, it`s "German". So, are you satisfied now?