Theme Completely Changed Problem

I had my theme set up via the photography demo, and it was perfectly fine. Suddenly overnight it reset itself and reverted to a different look (I think the high end default is the closest to what it looked like). Basically all the high end settings changed, however, all the pages and posts seem to have stayed the same. I was able to revert some of our settings (ie. move the header menu to the side etc), but I am stuck with the background colors, and the menu colors. I tried the color customizer and many things with no luck. I need the general look of it to revert to the photography demo -with my content obviously. Mainly I need the menu to change back to being black and the background on all the pages to revert to black as well. (I am including an image of what the menu looks like now, unfortunately cannot upload a second photo to show the background of the pages being white) I don’t want to re-upload the theme since we will lose a lot of content. It also looks like all the custom CSS codes are gone in the high end settings section.

The slider revolution is also hidden behind the menu on several of our pages, which was not an issue before. How can I fix this as well?

I was also wondering what could have caused the erase of all our settings, since we lost our social media links and the general overall settings. It will be incredibly frustrating if this happens again.

Update: The overall font for the site has also seemed to change. I don’t know what the original font for the photography demo is. Can I also get assistance on that?

Thanks