如果你做不到，儘快連絡我們。

If you can't make it, call us as soon as possible.

Source: Tatoeba

Sentence Composition

1 如果 rúguǒ
  1. if
  2. in case
  3. in the event that
=2 你 nǐ you (informal, as opposed to courteous 您 nín)
=2 你 nǐ you (Note: In Taiwan, 妳 is used to address females, but in mainland China, it is not commonly used. Instead, 你 is used to address both males and females.)
3 做不到 zuòbùdào impossible
4 儘快 jǐnkuài as quickly as possible; as soon as possible
5 連絡 liánluò variant of 聯絡 liánluò
6 我們 wǒmen we; us; ourselves; our