老师让我们坐下听课。

Lǎoshī ràng wǒmen zuòxià tīngkè.

The teacher asked us to sit down and listen to the class.

请坐下。

Qǐng zuòxià.

Please sit down.

请坐下休息一下。

Qǐng zuòxià xiūxi yíxià.

Please sit down and rest a bit.