.overlay::after {
  content: "";
  background: url('../images/background1.jpg');
  opacity: 0.1;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  position: absolute;
  z-index: -1;   
}
.overlay {
  display: block;
  position: relative;
  width: 100%;
  height: auto;
  left: 0;
  top: 0;
}