Scale image on mobile version

As @bycrawford said you should reduce the number of grid rows, but since you have images layered in that section you may want to adjust their position first.

The reason that the image takes up the full height of the screen on mobile is that you have this code in Custom CSS that is forcing the section to be full height (100vh):

@media screen and (max-width: 767px) {
section[data-section-id="64e54f9bb946601f10e2af9e"] {
    min-height: unset !important;
    height: 100vh;
}}

If you remove that the section height will then be set by the section settings of 33vh (small in the section settings) and by the contents of the section.

To summarise; remove code, rearrange images and reduce the number of rows.