@pedramnj, use wordpress language settings to change your site’s language. Plugin then will use those language if it’s available in translations.
When I use “German” (= Deutsch), the language settings of wordpress, the plugin works fine. But when I switch to “German formal language” (= Deutsch (Sie)), the plugin uses English. Any help?
It’s because plugin has “de_DE” locale and not has “de_DE_formal”.
See here: https://github.com/garex/wp-testing/tree/368b6ae10f009443e4cc8ba2675c7589433fe7b5/languages
As I see here https://translate.wordpress.org/projects/wp/dev/de/default in wordpress de_DE differs from de_DE_formal mainly by using “Du” vs “Sie”.
If you need current de version in plugin, then you can just copy paste file wp-testing-de_DE.po into wp-testing-de_DE_formal.po
And this should be done on each plugin’s update.
Another way — you can try to “translate” (mainly just adapt) wp-testing-de_DE.po into wp-testing-de_DE_formal.po and send it to me — I will then include in in next release.
To translate use program like poEdit — it should be availalbe in windows/max/linux.