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

.header-box {
  padding: 14rem 0;
  max-width: 550px;
}

@media only screen and (max-width: 600px) {
  .header-description {
    width: 90%;
    margin: 0 auto;
  }
}