Solved How to translate DU?

Hello,

I'm trying to translate DU child theme into Vietnamese and would like to ask some help:

1. I've downloaded the .pot files as guided here: https://intercom.help/elegantthemes/en/articles/2434045-how-to-translate-the-divi-theme
2. And created /lang/theme folder under DU child theme, also upload the .mo file there. But nothing changed on frontend.
3. I also use a translation plugin called Loco Translate, but it doesn't recognize the translation file and send me this message: Error: Translation set not known in Divi Ultimate

Did I do something incorrectly, or the DU theme is not ready for the translation?

 

I'd like to change several parts, like the post's meta and comment sections, and the search section. I don't want to change the site language from the default en_US to another, but some specific sections.

I actually can do this to some plugins, but still not able to do with Divi's child theme

 

Thank you