我先走？ 你先走？

have to go/have got to go/ need to go      我先走了

Got to go  before I miss my train to shanghai, it is lovely to see you ,as always.

我得先走了，不然赶不上去上海的火车了，和往常一样很高兴见到你

After you, please!

你先走。

After you with suger。

你先用糖，我后用