You can add this CSS code to hide that menu:
.secondary-navigation, .menu-toggle {
display: none;
}
Of course, that option doesn’t remove it but just hide it.
To try to remove it, since I think you don’t want to get rid of the Max Mega Menu
you can try to go to Appearance > Menus and find the menu on top and check if it has any Display location checkbox marked so you can uncheck it.
I didn’t find any options for a Secondary menu on its documentation so it’s kind of weird.