For example, when we buy, the selling price of EUR/USD is 1.4252, and the corresponding buying price is 1.4250. When we sell, the transaction price is based on the purchase price. Therefore, if you don't want to lose money at this time, the price should rise by at least 0.0002. If you keep going up, you will make a profit.
Bulls buy first, bears sell first. Usually we trade stocks long, that is, you can only buy them first and then sell them.