Is day trading crypto a fool proof plan? My friends think it is.....

My friends showed me their new fascination with day-trading and they seem to think it's a assured way to make money. They have the trading platform with the red and green candles and the crypto that they convert to stable coin etc

I have some questions to ask because I am scratching my head over here.

1) How does someone not perpetually make money if they have bots / trade when they are only in the green, or just hold until it goes green? How are people losing money if this is the case?

2) My friend says that he has a crypto visa card that he can purchase stuff with from his crypto wallet and he does not get taxed on any of the gains he makes because he has not withdrawn into his bank account. Is this a way to dodge taxes and just spend the gains you have made in one trade? Lets say you profit $80 dollars in a trade, could you just go the store, buy something worth $80 and then go back and do the same thing again? Could you just constantly making small amounts of money selling only when green and then make purchases in real life?

Where do people lose in this, I don't understand....

Thanks in advance