.col-sm-5.overlay-column{
  padding: 20px;
  background: rgba(0, 0, 0, 0.5);
  color: white;
}

@media (min-width: 768px) {
  .overlay-row{
    position: relative;
  }
  .col-sm-5.overlay-column{
    position: absolute;
    height: 100%;
    z-index: 1;
  }
}