index.css

body {
   background-color: #717171;
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen',
    'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue',
    sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

code {
  font-family: source-code-pro, Menlo, Monaco, Consolas, 'Courier New',
    monospace;
}

#sidebar{
  position: fixed;
  height: 100%;
}

#sidebar ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
  width: 250px;
  background-color: #f1f1f1;
}

#sidebar li a {
  display: block;
  color:#000;
  padding: 55px 40px;
  text-decoration: none;
}

#sidebar li a:hover {
  background-color: #555;
  color: white;
}

.active {
  background-color: #4CAF50;
  color: white;
}

#para{
  position: relative;
  padding: 200px;
}

* {box-sizing: border-box;}
body {font-family: Verdana, sans-serif;}
.mySlides {display: none;}
img {vertical-align: middle;}

#heading{
  text-align: center;
}

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

/* Caption text */
.text {
  color: #030303;
  font-size: 15px;
  padding: 12px 12px;
  position: absolute;
  bottom: 10px;
  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: 15px;
  width: 15px;
  margin: 0px 5px;
  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}
}

.button {
  background-color: #4CAF50;
  border: none;
  color: white;
  padding: 16px 32px;
  text-align: center;
  text-decoration: none;
  display: inline-block;
  font-size: 16px;
  margin: 20px 490px;
  transition-duration: 0.4s;
  cursor: pointer;
}

.button1 {
  background-color: white; 

  color: black; 
  border: 2px solid #4CAF50;
}

.button1:hover {
  background-color: #4CAF50;
  color: white;
}