at casino, 80% odds is on house favor. I'm not really like to play at casino, even at landbased casino, i only play in slot.
The house edge is nowhere near the levels that you put in your post, if you are playing in a European roulette the house edge is only 2.7% and if you are playing in an American roulette than the house edge is 5.26%, despite the small size of this house edge mathematically this means that over the long term it is going to be impossible for you to beat the casino, but if you are playing for fun, as you should, then this is not a problem at all and you can gamble with an amount of money that you can afford to lose.
Regardless of the house edge, the fact that its a gambling means the chance to win depends on your strategy and luck.
You can choose to bet with a low payout but high chance to win or with high payout but low chance to win so it really depends on your strategy.
Like other games you need to be lucky in order to win because that plays a big part in gambling.