Does somebody know how to claim the coins you won in a game? I just can't figure it out and the warzone wikia doesn't say anything about it as far as I know.

Coins won can be utilized in game only. Coin withdrawal has been ended some time back ( https://www.warzone.com/blog/index.php/2017/08/ending-coin-withdrawals/) and you can use coins earned for buying Color or Membership or Clan or name change.

@John Titor I mean that after a match with coins I haven't had gotten them like you do when you watch ads. It's really weird.

It automatically adds them to your account, there's no need to claim. You can view recent coin transactions on this page: https://www.warzone.com/Coins/Transactions

that doesn't seem to happen.

Are you sure you won a coin game?

Can you link the game you won?
Also, maybe you got the coins but also paid the buy-in, resulting in receiving less than you thought in net earnings?

Did you possibly win a game in a coin tournament? This doesn't give you coins unless you rank high enough at the end of the tournament (check the tournament settings to see which places receive a coin prize).