我要还钱给你。

Wǒ yào huánqián gěi nǐ.

I have to return money to you.

我还有很多作业没做。

Wǒ hái yǒu hěn duō zuòyè méi zuò.

I still have a lot of homework not done.

我明天要把书还给图书馆了。

Wǒ míngtiān yào bǎ shū huán gěi túshūguǎn le.

Tomorrow I have to return books to the library.