Some unexpected errors with top menu and categories

Hi, i bought a license for GirlsBook yesterday. This theme is awesome but i met some big problems with a menu bar after slides. My menu bar just broken, don't know how to explain because i haven't done any changes in header yet.

So, i started to change all website how i need and after some plugins were installed i saw that some errors occured with the top menu bar. Firstly i saw that the first link which was called as "Home" changed as "Login" ("Prisijungti" in my language). After that i saw that my categories isn't here anymore. I don't know what exactly happened... My menu bar just changed "main page" link to "login" and categories was disabled. What i suppose to do to get my categories back?

Site url: http://rankdarbiai.in

BTW, i even tried to reupload this theme as a default, nothing changes... Just replaced all theme files with original and non-edited ones but the problem is still there.

Sorry for triple post, i disabled all my plugins and nothing happens. Problem like that i have my very first time, it looks like that my top menu bar changed by itself to from home hyperlink to login. And categories just disappeared, there is no logical reason for that change. Please help...

PROBLEM SOLVED!