Hello,
Try to add the next code in Theme Options > Theme custom CSS > Custom CSS for mobile:
.null-instagram-feed .instagram-pics.instagram-columns-3 li {
width: 50%;
}
.null-instagram-feed .instagram-pics.instagram-columns-3 li {
display: none;
}
.null-instagram-feed .instagram-pics.instagram-columns-3 li:first-child, .null-instagram-feed .instagram-pics.instagram-columns-3 li:nth-child(2) {
display: inline-block;
}
> https://gyazo.com/9fbcca1613cd267098ad75ac2e820c3c
Regards