@media only screen and (max-width:768px){
.first img{
  width: 100%;
  height: auto;
}
}

@media only screen and (min-width:1190px){
  .first img{
    width: 1190px;
    height: auto;
    display: block;
    margin: auto;
  }
}

@media only screen and (min-width:768px)and (max-width:1190px){
  .first img{
    width: 100%;
    height: auto;
  }
}