Hi,
Thank you for your work!
I took out $string['appstoredescription'] since that was not translated.
I also changed $string['core.settings.reportinbackground'] since it was missing '; (translating off line is dangerous).
The strings for the mobile app are only included with a new release of the app, so you might need to wait a while before you see the app translated.
I have send you a private message to become language pack maintainer for Vietnamese. There are a lot of strings pending for approval, so that would be an easy win for the Vietnamese language pack if you could approve them.
Kind regards
Koen