.desk{
  width:300px;
}
.div-only-mobile{
  width:300px;
}
@media screen and (max-width : 3000px){
  .div-only-mobile{
  visibility:hidden;
  }
}
@media screen and (max-width : 706px){
 .desk{
  visibility:hidden;
  }
 .div-only-mobile{
  visibility:visible;
  }
}