body{
  background: url(../img/bg4.png) no-repeat center center fixed;
  -webkit-background-size: cover;
  -moz-background-size: cover;
  background-size: cover;
  -o-background-size: cover;
}

@media (max-width: 991px) {
  .section {
  margin-top: -50px;
  }
}