I would like to know how to start dropshipping on Amazon with Aliexpress? I've heard that many dropshippers are doing it now, but I can't figure out if it's legal? And how much can you really make on it?

The percentage of sales is calculated individually, so it is impossible to answer how much you will earn in this way. However, in general, it is possible to earn good money, if everything is properly organized. And as far as legality is concerned, of course, such drop shipping is absolutely legal, many people are involved in it. Read here how to dropship on Amazon from Aliexpress https://easync.io/articles/dropshipping-from-aliexpress-to-amazon/.