这位是负责市场管理的同事。

Zhè wèi shì fùzé shìchǎng guǎnlǐ de tóngshì.

This is our colleague from in charge of marketing.

这次让我来负责买菜吧。

Zhè cì ràng wǒ lái fùzé mǎicài ba.

This time let me be in charge of buying vegetables.

我负责处理投诉。

Wǒ fùzé chǔlǐ tóusù.

I'm in charge of handling complaints.