Add this code to the Custom CSS field on the Style tab of your Reviews widget’s settings:
@media (max-width: 500px) {
.swiper-slide .es-review-container {
min-height: 300px !important;
}
.es-review-content-container {
flex-grow: 1;
}
.es-reviews-images-container {
grid-auto-flow: row;
grid-template-columns: 1fr 1fr;
}