I cancelled the cs:go gift because i was not connected on my steam account.
I bought the key on g2a.
" tis Cyka is dangerous " is the name on steam of the person who send me the gift
this was this link to activate the gift : https://store.steampowered.com/account/ackgift/AC5111A582799720?redeemer=
g2a payement proof : http://gyazo.com/8523f7bc18a22663c0c8c223d4b63fda