What can i do?

Wait, he gifted you an Origin key? Against the rules.

1 - Contact support.
2 - Report the giveaway.
3 - DO NOT mark as received.
4 - After seven (7) days, mark as not received.
5 - Enjoy seeing the dumbass getting banned. :P

Don't mark it as received, wait 7 days, mark it as "not received".

You will get a suspension if you mark it received and don't add it to your Steam account (which you obviously can't do).

Also contact support and report the giveaway.

Of course you can set a NO, this is STEAMgifts and the rules are very clear about it:

All games must be Steam-redeemable.

Actually he didn't sent the gift because it was not a gift and not even a Steam-redeemable key.

Wait 7 days and then mark it as not received. And maybe contact support about what to do. If you mark it as received you won't have game in your Steam library and you will get suspended. But you can always ask support. Origin is against rules but atleast he gave you the game... Ask support.

Aha! After 7 days and i will feedback "NO". OK, Thank You.

I dont want to he getting banned. I will "NOT mark as received"