The amount of gambling losses you can deduct can never exceed the winnings you report as income. For example, if you haveR$5,000 in winnings butR$8,000 in losses, your deduction is limited toR$5,000. You could not write off the remainingR$3,000, or carry it forward to future years.
In the unlikely event that a gambler were to win a sum of money that the casino was unable to pay, the casino would likely work with the player to come up with a plan to pay the winnings over time. This could involve paying the player in installments, or the casino may seek outside financing to cover the payout.