I mean, as i know, when you withdraw BTC, the transfer take minimum 15 minutes or more.
No, that is not true.
This is normal and not a miracle. You might have been lucky or you don't understand how Bitcoin works. Either a miner saw your transaction when you broadcast it and mined it in a block that was found shortly after you broadcast it, OR your wallet is showing the transaction before it confirms. Nothing special, nothing new.