1。班门弄斧

2。心有余而力不足

3。 一言既出驷马难追

4。对牛弹琴

1.班门弄斧：teach one's grandmother to suck eggs;display one's slight skill before an expert

2.心有余而力不足：the spirit is willing, but the flesh is weak；unable to do what one hopes to do

3.一言既出，驷马难追：what is said cannot be unsaid;a word once spoken cannot be taken back even by a team of four horses

4.对牛弹琴：Cast pearls before swine;preach to deaf ears;talk to a post;whistle jigs to a milestone

以上译法中第一种比较推荐！