I can't make sense of it.

这个我弄不明白。

Exactly.

完全正确。

It's inevitable that he'll find out about it.

他无可避免地会发觉此事。

Do you know what I'm talking about?

知道我讲的是什么吗？

I think you are getting off the subject. Could we get back to the main point, please?

我觉得你跑题了。 我们能不能回到主题上来？

How about cleaning up a bit around here?

你是不是该把这儿收拾一下？