layout form

To get that specific layout, you’ll also need to modify how the fields are nested in fieldsets in addition to modifying the CSS code. You can see how I do this in one of my themes here:

https://github.com/NateWr/luigi/blob/master/includes/integrations/restaurant-reservations.php

And the corresponding CSS which uses a layout similar to what you describe:

https://github.com/NateWr/luigi/blob/master/assets/src/less/plugins/restaurant-reservations.less#L186-L216

If you’re not very comfortable working with code, I’d encourage you to hire a developer who can do it for you with the proper handling of media queries for small screens.