First of all....Impressive amount. Congrats
this is a very good question. Where are you based, in which country?
Probably you should talk with a local tax advisor for a clear explanation.
Of course he need to be confident with crypto... I will made a verify also for local rules regarding gambling taxes.
However if you spend directly bitcoin ( please correct me if I am wrong) you don't need to pay any tax on this... but of course if you don't have a job and tomorrow you are driving a Ferrari it's clear that some local regulators could have a look on your "real" activities...
I thought the tax to be paid will be deducted by the gambling site or am I wrong?
Why not want to pay tax? It is better you pay your tax.
Some people are avoiding tax with decentralized exchanges and selling directly to someone.
No, they are not paying anything. Also using decentralized exchanges could be a solution but If your bank account receive a massive amount, it's clear they can freeze your account, asking explanations, highlight the issue with local authority ....