Need a Navigation Menu Fixed

Another contractor programmed our dynamic navigation menu but it's still not working properly. Now we're looking for someone to fix his mistakes or just start from scratch and build the menu correctly.

The menu was programmed using HTML and CSS. Something is wrong with the CSS code because the menu appears differently (and incorrectly) on different devices. It's supposed to adjust to whatever browser/device it's being viewed on and look the same everywhere.

So that's what we need help with. I'll supply the existing code - you provide the talent and know-how to get this project done correctly this time around.