#header {
  background-image: url(https://oscarbergstrom.netlify.app/public/images/portfolio_background.jpg);
}
/*-----------------------------600px-----------------------------*/
@media only screen and (max-width: 600px) {
  #header {
    background-image: url(https://oscarbergstrom.netlify.app/public/images/small-screens/portfolio_background.jpg);
  }
}