I was trying to translate the mod in italian Via resouce pack but the file it_it.json was already there so I opened it and it was in English
I tried zh_tw and ja_jp and them were in English too, i don’t know if this is an issue

Half a known problem and half not a problem. By setting up Crowdin to handle translations from users, lang files for all the languages were created (defaulting to english).
The existing ones (jap, ru, cn) were also lost, but they should be restored when the next Crowdin merge happens.

Use https://crowdin.com/project/ars to submit the translations, it will help working in team or discussing if others want to help as well. Bailey doesn't check it often tho.