Try to add this to your style.css at bottom
@media screen and (max-width: 767px) {
/* RADIUS SEARCH */
.radius_h2 {display:none;}
#home-map #map_radius_here, #listing #map_radius_here {top: 0; left: 0; width: 100%; border-radius: 0; padding: 10px 5px;}
#map_radius_here input {width:45px;}
#listing #map_radius_here .radius-show-now.radius_locate, #listing .radius_locate {width:30px;overflow:hidden;padding:0;text-align:center;color:#2196F3;}
#listing #map_radius_here .radius-show-now.radius_locate:before, #listing .radius_locate:before {width:30px;height:30px;display:block;background:#2196F3;color:#fff;}
}