Hello,
Do you want to translate your site to the Vietnamese language? Follow the instructions https://xstore.helpscoutdocs.com/article/30-base-theme-translation and translate both: XStore theme and XStore Core plugin.
Besides we already have translation for the XStore theme https://www.8theme.com/glotpress/projects/xstore/xstore-theme/vi/vietnamese/ So, you can download that and use it on your site.
Regards
