.container {
  max-width: 800px;
  background-color: black;
  margin: 0 auto;
  text-align: center;
  position: relative;
}
.container div {
  background-color: white;
  width: 100%;
  display: inline-block;
  display: none;
}
.container img {
  width: 100%;
  height: 400px;
}

button {
  position: absolute;
   opacity: 0.5;
   background-color: white;
  color: black;
  border: 2px solid #4CAF50;
  border-radius: 50%;
  border: 1px solid green;
}

button:hover {
  background-color: #4CAF50; /* Green */
  color: white;
}

button {
  -webkit-transition-duration: 0.4s; /* Safari */
  transition-duration: 0.4s;
}

.next {
  right: 5px;
}

.prev {
  left: 5px;
}