body{
  background-image: url("https://cdn.sakaflix.de/saka_mediathek.jpg");
  background-size: cover;
  background-repeat: no-repeat;
  background-attachment: fixed;
  }
  
  div.well{
    height: 250px;
  } 
  
  .Absolute-Center {
    margin: auto;
    position: absolute;
    top: 0; left: 0; bottom: 0; right: 0;
  }
  
  .Absolute-Center.is-Responsive {
    width: 50%;
    height: 50%;
    min-width: 200px;
    max-width: 400px;
    top: 0; left: 0; bottom: 0; right: 0;
  }