在 + Place/Location + Verb
在 (zài) is a preposition used to indicate location, position, or the setting of an action. It introduces a prepositional phrase that tells where something happens or exists. The phrase formed with 在 typically appears before the verb in a sentence.
他在图书馆看书呢。
Tā zài túshūguǎn kàn shū ne.
He's reading in the library.
我们在公园里散步聊天。
Wǒmen zài gōngyuán lǐ sànbù liáotiān.
We took a walk and chatted in the park.
她在家等你好长时间了。
Tā zài jiā děng nǐ hǎo cháng shíjiān le.
She has been waiting for you at home for a long time.