The whole template I have translated are installed 2 languages Polish-English
everything works does not translate the category .. ?? (after adding a new category similar situation)
The admin writes and changes the translation but after refreshing it returns to English
Please help where is the problem ..? 

@44-55-66
There use to be bug with categories (problem with osclass) where category names remain in lately added language.
If you look on osclass forums, you will find solution, there is one thread from Teseo reagarding this problem.

I found the same problem but I can not see the solution ..? what should I do..?
https://forums.mb-themes.com/veronika-osclass-responsive-theme/subcategorie-not-in-french-but-my-website-is-in-french/msg8059/#msg8059

Here is the solution:

https://raw.githubusercontent.com/teseo-2014/Osclass-develop/develop/oc-includes/osclass/model/Category.php

change these category.php with the old category.php and everything works fine