teach the dog to bark字面意思是“教狗怎么叫”，引申为“多此一举”。

【例句】
He is a pianist and you want to teach him how to play the piano. Don't you know that you are trying to teach the dog to bark?
他是一个钢琴家，而你却要教他弹钢琴。难道你不知道你是在多此一举吗？

His actions are a bit teach the dog to bark.
他这么做有点多此一举了。