Thanks for contacting us.
Alright, Let me explain to you how it works and the possible ways to fix it.
1- Why, is this happening on mobile? The thing is mega menu has columns and columns based on the 2nd sub-menu items see the image: https://postimg.cc/hJ0B9Bcv then the rest of the sub-menu items you want to show in these columns you will add like this: https://postimg.cc/7frKyTgv so on the desktop the menu will be open on hover but as you know mobile devices don’t have the hover functionality which is why on mobile the column sub-menu item appears and then it will show the rest of the menu items its default functionality. I hope you understand.
2- First, Actually the thing is the requirement you want is not possible with the theme options. But it can be possible if you create 2 menus and assign the location of both menu the same see image: https://postimg.cc/D8pBDYyZ then both menu shows at the same time on desktop and mobile. Then you need to hide 1 menu from the desktop and 1 from mobile. for this you need to pick the class/ID of the menu how can you do that see the image: https://postimg.cc/p5Z1pWHY this way you be able to pick the class/ID of the menu.
Simply copy the class/ID and then add the CSS code for “Display:none”
This is the only possible way if you are not able to add your custom code in the Appearance >> Theme Options >> Skins >> Custom CSS by using the class/ID then you can find the way from google or any other website you want.
I hope you understand.
3- Secondly, Once you create different menus and assign the location of the menus different from the Appearance >> Menus you can simply choose the menus from the theme options >> menus >> mobile menu >> the menu you want to show on mobile see the image: https://postimg.cc/gnxTYP7R
4- Further, if you want anything else, then you can proceed to create a feature request on our forum here: https://www.portotheme.com/forums/topic/feature-request/ so that our development team will notice it and remember it while working on the theme update. I hope you understand.
Have a nice day.