div#colonna-1{ float: left;
    width: 50%;
 padding: 0 2%
   }
#contenitore-1-2 {
   float: left;
width: 100%;
}

#contenitore-2-3 {
   float: right;
}
#colonna-2{
     float: right;
    width: 45%;
    padding: 0 2%
  z-index:3  }
#colonna-3{
     float: right;
    width: 29%;
    width: 33%;
    width: 29%;
    padding: 0 2%
    }