19 ETH is a lot of money and I think that Cloudbet hostaging your money is alarming. Although, I can understand why they might be hodling back that money, money laundering can be done through crypto gambling so they might be taking some precautions that you are not laundering the money.
Well, yes, but i deposit just 1ETH, and won 20ETH. How is that laundering

Please tell us more about the case? You made 20x profit from a single bet or series of bets? It would me more helpful if you can provide link to screen shots of your bet history. Recently cloudbet took almost 2 months to release a big win but they did and initially I gave them negative feedback but after they paid in full I withdrew my negative trust.
What I think is they are lacking in customer care which is why they are taking so much time to make big payments because they have to make sure about any money laundering or potential loophole in their system which can be devastating for a casino.
I suggest you to keep little more patience and hang in here with regular reminders for cloudbet. I am optimistic that you will get you money if you have done nothing wrong. I am repeating that posting your bet history up front will make you case more stronger.
It’s not important to know on how many bets he made to win that profit. Cloudbet allow the 1ETH withdrawal which means his method is legit since most probably he do the same way to get the rest of 19ETH profit. Cloudbet is known for not paying high roller balance although some of it is an isolated and already solved but still this is an interesting case if he can provide more evidence.