本末倒置 -------- put the cart before the horse

例句：
A: Could you lend some money to me again?
请再借一些钱给我好吗？
B: Nope, no way! You should return me the money borrowed from me last time, or you'll put the cart before the horse.
不，不行！你应该把上回向我借的钱还给我， 否则你就本末倒置了。