Cyrillic – Google Font

Hello and thanks for the great job – theme is really cool.

I’m no expert, and after clean and default installation I’m having a problem with cyrillic fonts. Open Sans is showed in Russian in the menu and in the footer, but not in the body. In the page body it becomes Arial. Also in some other places (like for example Revolution Slider) Google Fonts are not displayed for cyrillic. English is OK everywhere. What can be done here? Thanks in advance!