I'm doing it because yesterday I posted an update saying that I was "The New Head Waiter" at the restaurant.

我这么做是因为昨天我发了一条更新说我是餐厅的“新领班”。

I saw your post yesterday.

我昨天看到了你的帖子。

I tried to explain the book to my brother yesterday.

昨天我试着向我哥哥解释这本书。