The process is:
Pay single payment of 0.01BTC for wallet verification. (Around 500euro)
Pay single payment of 0.03BTC for premium account. (Around 1,500euro)
Pay another 0.1BTC (20% tax of your 20k "winnings which is around 4,000euro)

All that so that you might withdraw your "winnings" of 20k + your deposits.

They keep asking money... In the end, they will probably tell you that you won by accident and that you can't withdraw anything.

winxtrade.com is a scam site and must be avoided at all costs