Larger & layered navbar menu

Hello, 

I am wondering if it is possible to have much larger drop-down navigation menu, like the ones of https://www.who.int/ or in another style https://www.gatesfoundation.org/.

I have a lot of info to feature in the navbar and the single lines, even with the drop-down folders option is not enough. 

Thank you all for your help.

Best regards, 

Léa

What is your site url?