不好意思，我有事情要先离开了。

Bù hǎoyìsi, wǒ yǒu shìqing yào xiān líkāi le.

I'm sorry, I have to attend to something and must leave.

你什么时候离开北京？

Nǐ shénme shíhou líkāi Běijīng?

When will you leave Beijing?

你放心，我不会离开你的。

Nǐ fàngxīn, wǒ bú huì líkāi nǐ de.

Don't worry, I won't leave you.