Gallery Thumbnail

I’m wanting to make the gallery in a list block have a single thumbnail (instead of them all showing), and then be able to click on the thumbnail and have the full gallery to scroll through. Using list with deletable elements and vertical cards. Added this to the header page but I’m definitely doing something wrong and i’m new to this

#list2 .gallerycontainer { height: 100px; overflow: hidden; } #list2 .gallerycontainer .sw-img:not(:first-child) { display: none!important; } .gallery-container { display:none; } .gallery-container:first-child { display:block; }