Home Page Drowdown Category didn't work

Ok, I thought I have solved the problem by myself. It actually still existing. When I click HOME on the main menu, then there is no Category dropdown anymore. Also, when I click the other Demo home page on DEMO it goes direct to your demo website/link.

I have purchased several themes from other authors and this kind of thing is never happened. How to disable the link to your demo site? and how to make the category dropdown work?

Thanks