body, html {
  height: 100%;
  margin: 0;
}

.bg {
/*--  background-image: url("hintergrund.jpeg"); */
  height: 100%;
  background-position: center;
  background-repeat: no-repeat;
  background-size: cover;
  opacity: 0.85;
}

.caption {
    position: absolute;
    left: 0;
    top: 60%;
    width: 100%;
    color: #000;
}

img.vcard{
  max-width: 300px;
  margin-left: 20%;
}

@media (max-width: 840px){
  img.vcard{
    max-width: 80%;
    margin: auto;
    display: flex;
    justify-content: center;
    align-items: center;
  }
  .caption{
    top: 50%;
  }
}