CSS for no background image on small devices

please use a child theme or a custom css plugin for the css edits;
https://codex.www.ads-software.com/Child_Themes
https://www.ads-software.com/extend/plugins/search.php?q=custom+css

add the background image css for instance into a @media query like:

@media screen and (min-width: 960px) {
  .whatever { background: ..; }
}

or hide a background with a @media query like:

@media screen and (max-width: 960px) {
  .whatever { background: none; }
}

adjust the numbers

Thanx Al…. That worked, yes, I am using my child theme.