Subject + 正(在) + Verb
The adverb 正 (zhèng) indicates that an action is currently in progress, similar to the English present continuous tense. It is often used together with 在 to form 正在, meaning 'in the process of.' For example, 正在寻找 means 'currently searching for.'
你别打扰他,他正写作业呢。
Nǐ bié dǎrǎo tā, tā zhèng xiě zuòyè ne.
Don't disturb him; he's doing his homework.
我打电话的时候,她正吃午饭。
Wǒ dǎ diànhuà de shíhòu, tā zhèng chī wǔfàn.
When I called, she was eating lunch.
外面正下着大雨,我们等一会儿再走吧。
Wàimiàn zhèng xià zhe dà yǔ, wǒmen děng yíhuìr zài zǒu ba.
It's raining heavily outside; let's wait a bit before we go.