Mobile Picture not Resizing

Site URL: https://gecko-flounder-tpbf.squarespace.com/config/

I would love for the pictures on my home page and about page to resize in the mobile format.  Can anyone help me with this. 

Add to Home > Design  > Custom CSS

/* resize homepage banner */
@media screen and (max-width:767px) {
.homepage #page section:nth-child(2) {
    min-height: 20vh !important;
    height: 40vh;
}
}