Wordpress Mega Menu change

I require an existing Mega Menu to be changed from it's current drop down style, to be full width when used in a desktop view.

I require the same menu and sub menu structure to stay in place - this is solely a design change. It also needs to remain responsive for different devices.

Ideally complete within 12 hours.

Current website with existing menu: https://tinyurl.com/bdhfmfxw

Sample website - target menu style: https://tinyurl.com/msdkztm6 / https://tinyurl.com/yckujawr