I have usd those following codes form Victoria. I think it works perfectly. And thinks for your Reply

@media only screen and (max-width: 479px) {
.av-horizontal-gallery .av-horizontal-gallery-inner {
height: 50vh !important;
}
}
@media only screen and (min-width: 480px) and (max-width: 767px) {
.av-horizontal-gallery .av-horizontal-gallery-inner {
height: 100vh !important;
}
}

could you help me with that？