How to make Mega Menu full screen width?

Hi,

How can I make my mega menu 100% full screen width? Why is there no option in the megamenu to do this?

Currently it only spans up to the container width.

I have tried the following CSS on my .megamenu

width:100vw!important;
position: fixed!important;
top: 100px!important; (This aligns it to the bottom of the navigation)
left: 0!important; (This aligns it to the beginning of the navigation menu, but not the left edge of the screen)

The page I need help with: [log in to see the link]