Banner images resizing

Site URL: https://www.intlschooloftheprophets.com

I need all of my banner images to fit within the mobile aspect of the website but  don't seem to be fitting properly after trying different codes. Can someone help me please

Add to Home > Design > Custom CSS

@media screen and (max-width:767px) {
.homepage section:first-child {
    min-height: unset !important;
    height: 70vh;
}
}