Hello,
While mega menu is a way to fancy up a menu, you need to do a lot of extra work to create a two column layout for a regular menu.
I would need to split out the drop down menu items from the main menu, put them in a separate menu so I could load them in a module to load them in a column within mega menu.
Your development team should consider putting some extra effort in the regular dropdown menus. They do not even function responsively as they are, hence the reason I'm having an issue with the dropdowns in a single row.
Regards,
John