html,
body {
   overflow-y: auto !important;
   /* optional, if horizontal scroll isn't needed: overflow-x: hidden; */
}

.wap-frontend .wap-button-style-preset__preview-btn {
   position: fixed;
   width: 45px !important;
   height: 45px !important;
   bottom: 100px !important;
   right: 37px !important;
}