If i set a language for my article or category then are there not visible in backend, how it's posible to get this elements visible? I tried to filter items but there are still not visible...

What Joomla! and K2 versions do you use?
Check if you see them when you do not have any filter selected.

K2 Version: 2.6.7
Joomla: 2.5.16,

Filter is not touched, but also if i try to filter then are they not vissible, but if i set through DB "*" as language then are this elements vissible, maybe k2 bug?

I tested with more installations, is the same problem.

Is it possible to provide us access to your backend to check it out?

Sent it through the contact form here: getk2.org/contact-us