說得頭頭是道
to be able to talk in a confident way that makes people think you are good at what you do
You can talk the talk, but can you walk the walk? (= can you act in a way that matches your words?)你說得頭頭是道,可你能做到嗎?
釋義來自《牛津高階英漢雙解詞典》第 9 版