To remove (disable) the Overlay Scrolling:
sudo nano /etc/environment
Add the following line:
GTK_OVERLAY_SCROLLING=0
Hit ctrl+x to exit, hit the Y key to say yes to save, then hit the Enter key to save under current configuration.
To get steppers back, you must use a Gtk Theme that offers them.
If you just really love the Zorin Themes, I can probably create a theme hack for you.
In the meantime, let's give you the ability to widen the ones you have, in case you would like to.
Hit ctrl+h in your home folder to reveal hidden files and folders. Navigate to .config then into gtk-3.0. Right click an open area in the desktop and Create New Document.
Name it gtk.css
Open the file and paste in
scrollbar {
-GtkScrollbar-has-backward-stepper: true;
-GtkScrollbar-has-forward-stepper: true;
}
scrollbar slider {
min-width: 16px;
}
scrollbar.horizontal slider {
min-height: 16px;
}
Adjust the size in px as desired.