But it seems it need proof reader or something. I am not quite sure how Crowdin works, need I also proof read the translation or something?

Crowdin supports several types of roles for its users:
translators, proof readers, managers, owners, … maybe even more (not sure)
I will only explain ...

Hello, I would like to contribute to Simplified Chinese translation. I've registered account on Crowdin and saved some translations. But it seems it need proof reader or something. I am not quite sure how Crowdin works, need I also proof read the translation or something?
A guide would be very nice ...