change height of background image (top section of a sub page) on mobile only

Site URL: https://www.taisdacosta.com/graphicdesign/memoiredelavenir

I've tried a few of the answers here but was not able to fix my issue.

Each of my sub pages has a background image at the top section. I'd like to change their height to "S" for the mobile version, but when I do so, it also changes it on desktop.

If not possible to set it to "S", I'd simply like them not to be in portrait mode but in landscape, like the rest of the images on the page.

Thanks!

Add this to Design > Custom CSS

@media screen and (max-width:767px) {
body.collection-5e1c9fe5e04db85bbc452446.view-item article section:first-child {
    min-height: unset !important;
    height: 60vh;
}
}