Drop-down menu issues on mobile. Theme: Interactive

Hi Everyone,

I am having issues with the drop-down menu on the mobile version of my website. Theme – Interactive (free version). This is the only issue I had so far, but it is a Big one since the majority of people are viewing websites from their mobiles first nowadays.

The problem is that when clicking on the hamburger menu item the drop-down menu appears with a transparent background which creates trouble viewing it. The menu items get mixed with the website content. 
When I am trying to add background to the dropdown it allows me so, but the change doesn’t show on the website.

Is it a bug? Anything I can do with it?

The whole website is ready and this issue is frustrating. I would appreciate the help!