get to the bottom of something 搞清楚某事，彻查某事

1. get to the bottom of something 搞清楚某事，彻查某事，对…寻根究底（to get an understanding of the causes of something）

例句：

There is clearly something wrong here, and I need to get to the bottom of it.

这显然有什么不对的地方，我要彻底搞清楚。

2. put up or shut up 要么行动要么就闭嘴，有点类似于网上流行的“You can you up, no can no bb（你行你上啊，不行别逼逼）”

例句：

You keep saying you're going to ask her out. Well, put up or shut up.

你一直说要约她去约会，那么，要么行动起来，要么就闭嘴。