From: https://www.w3schools.com/howto/howto_js_slideshow.asp

<!DOCTYPE html>
<html>
<head>
<meta name=”viewport” content=”width=device-width, initial-scale=1″>
<style>
* {box-sizing:border-box}
body {font-family: Verdana,sans-serif;}
.mySlides {display:none}

/* Slideshow container */
.slideshow-container {
max-width: 1000px;
position: relative;
margin: auto;
}

/* Caption text */
.text {
color: #f2f2f2;
font-size: 15px;
padding: 8px 12px;
position: absolute;
bottom: 8px;
width: 100%;
text-align: center;
}

/* Number text (1/3 etc) */
.numbertext {
color: #f2f2f2;
font-size: 12px;
padding: 8px 12px;
position: absolute;
top: 0;
}

/* The dots/bullets/indicators */
.dot {
height: 13px;
width: 13px;
margin: 0 2px;
background-color: #bbb;
border-radius: 50%;
display: inline-block;
transition: background-color 0.6s ease;
}

.active {
background-color: #717171;
}

/* Fading animation */
.fade {
-webkit-animation-name: fade;
-webkit-animation-duration: 1.5s;
animation-name: fade;
animation-duration: 1.5s;
}

@-webkit-keyframes fade {
from {opacity: .4}
to {opacity: 1}
}

@keyframes fade {
from {opacity: .4}
to {opacity: 1}
}

/* On smaller screens, decrease text size */
@media only screen and (max-width: 300px) {
.text {font-size: 11px}
}
</style>
</head>
<body>

<h2>Automatic Slideshow 1</h2>
<p>Change image every 2 seconds:</p>

<div class=”slideshow-container”>

<div class=”mySlides fade”>
<div class=”numbertext”>1 / 3</div>
<img src=”img_nature_wide.jpg” style=”width:100%”>
<div class=”text”>Caption Text</div>
</div>

<div class=”mySlides fade”>
<div class=”numbertext”>2 / 3</div>
<img src=”img_fjords_wide.jpg” style=”width:100%”>
<div class=”text”>Caption Two</div>
</div>

<div class=”mySlides fade”>
<div class=”numbertext”>3 / 3</div>
<img src=”img_mountains_wide.jpg” style=”width:100%”>
<div class=”text”>Caption Three</div>
</div>

</div>
<br>

<div style=”text-align:center”>
<span class=”dot”></span>
<span class=”dot”></span>
<span class=”dot”></span>
</div>

<script>
var slideIndex = 0;
showSlides();

function showSlides() {
var i;
var slides = document.getElementsByClassName(“mySlides”);
var dots = document.getElementsByClassName(“dot”);
for (i = 0; i < slides.length; i++) {
slides[i].style.display = “none”;
}
slideIndex++;
if (slideIndex> slides.length) {slideIndex = 1}
for (i = 0; i < dots.length; i++) {
dots[i].className = dots[i].className.replace(” active”, “”);
}
slides[slideIndex-1].style.display = “block”;
dots[slideIndex-1].className += ” active”;
setTimeout(showSlides, 4000); // Change image every 2 seconds
}
</script>

</body>
</html>

Automatic Slider (Working Code)