DW Page header (home) modified unexpectedly

Hello,
I have a page built on DW Page Modern: http://creativino.hu/ Thank you for the theme, it’s awesome.
As you can see, the first section A.K.A. the home section on my site now has a solid grey background and the menu is not working properly, since the menu titles are meant to be next to the logo, just like on your demo site.
The problem is that all these things happened out of nowhere. I checked the page last week when it worked properly, however I just discovered the changes now. I have really no idea what caused the problem. There were no significant updates, and absolutely no editing in codes. I don’t know if this is a common problem among DW Page users.
I had a look on the style.css but discovered nothing. I do not really want to edit the codes since nothing was changed and I am not a professional programmer.
 
I would be really happy if you could help me somehow.
 
Thanks,
Istvan