Link in navigation menu send user to different page if mobile?

In the past I’ve done this by adding 2 menu items named the same thing and hiding one when over a dimension (700px) and having one visible. Then when you cross the threshold you would reverse.

.menu-item-1 {
  display:block:
}
.menu-item-2 {
display:none;
}

@media all and (max-width: 699px) {
    .menu-item-1 {
      display:none:
    }
    .menu-item-2 {
    display:block;
    }
}

This is a bit simplified as i don’t know your menu item actual numbers or if they are inline or block or inline block, but this will get you close based on the idea.

You can add addition css to each menu item in the menu section (You might have to check the “screen options” in top right if you don’t see a css field.)