how it works on steam gifts?

No you are supposed to use the winning on your own account.
if you see some one with multiple wins of same game, report them, they are rule breaker.

As to how they do it, you dont need to know that ;)

You must activate the game if you won it. And you should not enter giveaways of games you already have.

You must activate it on your account.
If you see someone winning the same game twice please report them.

Apparently you haven't read the rules, read them before bad things happen.

Member for 5 months,won 4 gifts and then only ask this question?

I now the rules but i have seen a many people winning the same game twice, and i would little bit confused about that. But its everything clear to me now :)
Thanks :)

and no offense please :) is better to ask, like make a big mistake or not? :)

Ok :) thanks