1. I joined Learn2Trade, where they provide 5 suggestions per day, on whether to BUY or SELL.
2. I understand how to BUY and wait for the price to go up.
But I don't understand how you make money on SELL.
For example, let's say I believe BTC will go down. So I BUY BTC. And then I wait for it to go down and then SELL.
Don't I lose money?
The profits from both selling and shorting are the potential extra BTC you can gain if you buy at a lower price, compared to the current price.
If you sell Bitcoin, because you expect to buy back at a lower price in the future, you are leveraging the price of whatever it is for that you are selling your BTC. So if you leverage against USD, for example; You are "betting" that the Bitcoin price will fall, in relation to USD and therefore you can buy BTC at a lower price at a later time. This is the same thing as if you were shorting BTC by 1x. With spot selling you do not have a liquidation number hanging over your head. If you trade derivatives instead, you can increase that leverage as you see fit and short BTC for 10x or even 100x. But the danger here is the liquidation price will is always closer than you imagine. Even if you only short 1.5x, the moment BTC hits the liquidation price, you lose everything. Of course you could try to escape liquidation but your losses will be finalized and multiplied by the same leverage level that you chose.
So best thing to do is keep away from derivatives and options until you have understood how things work. There are testnets that you can use to short and long test BTC... For exampl Deribit Testnet.