Remove padding for image placed on top of banner on mobile? (Squarespace 7.0)

Site URL: https://cooperfoszcz.com/

Big amateur here, but I can't figure out how to remove the padding on an image placed on top of a banner for Squarespace 7.0. Specifically, I'm looking to change the landing image on mobile. Here's what I currently have: 

@media screen and (min-width: 640px) {#block-yui_3_17_2_1_1632180891068_6440 {
  padding: 0px !important;
  margin: 0px !important;}

https://cooperfoszcz.com/

Appreciate it!

Add to Design > Custom CSS

@media screen and (max-width:767px) {
section#pileposter>div {
    padding-left: 0 !important;
    padding-right: 0 !important;
}
div#block-yui_3_17_2_1_1632180891068_6440 {
    padding-left: 0 !important;
    padding-right: 0 !important;
}
}

then save & reload the site