Mobile Image resize - IDUMA

Site URL: https://bison-buttercup-bdpb.squarespace.com/

IDUMA template: 

Link:

https://bison-buttercup-bdpb.squarespace.com/ Password: 12345

(1) How to get the first image to display full width on mobile device?

I tried the following code but it leaves a grey background on mobile. 

@media screen and (max-width:640px) {
[data-section-id="5f249752d6f33d72e0925409"] .section-background img {
    width: 100% !important;
    height: auto !important;
}
}

(2) How to get the last image - height large on desktop but small on mobile?

Q1. Q2. Remove your code & add this code

@media screen and (max-width:767px) {
/* homepage first banner */
.homepage #page section:nth-child(2) {
    min-height: 20vh !important;
    height: 30vh !important;
}
/* last image */
[data-section-id="5f249752d6f33d72e092540f"] {
    min-height: 20vh !important;
    height: 30vh !important;
}
}