WordPress dashboard translation (admin section)

Hello, thanks for the great product! I have an issue, i can’t find the feature to translate the dashboard and admin section or just switch wp version while working in admin.

I have different users on the website (http://found.itsoknoproblem.com) and i want to make it multilanguage, when users can work with the language they want.

Right now (you can check it out, when i switch versions the description and all the translations work. When i log in and try to add a post, it switches to the default (Russian) language.
One more bug, i noticed is i can’t save preferences, when i set english as the default language under another user and go to the dashboard it switches back to Russian and when go back to the site it’s in Russian again. Please, help me find all the features! What can i do now?

https://wordpress.org/plugins/transposh-translation-filter-for-wordpress/