你们在谈什么？

Nǐmen zài tán shénme?

What are you talking about?

我们在会议上谈了很多事情。

Wǒmen zài huìyì shàng tán le hěn duō shìqing.

We discussed many things in the meeting.

我跟他谈了三个小时。

Wǒ gēn tā tán le sān gè xiǎoshí.

I spoke with him for three hours.