.big_circle {
  background-image: url("Resurces/Images/Business Simulations/1.jpg");
  animation: big_circle 5s infinite,
             change_background 15s infinite;
}

.middle_circle {
  background-image: url("Resurces/Images/Business Simulations/1.jpg");
  animation: middle_circle 5s infinite,
             change_background 15s infinite;
}

.small_circle {
  background-image: url("Resurces/Images/Business Simulations/1.jpg");
  animation: small_circle 5s infinite,
             change_background 15s infinite;
}

@keyframes change_background {
  0%, 31.5% {
    background-image: url("../Resurces/Images/Business Simulations/1.jpg");
  }
  33%, 63.5% {
    background-image: url("../Resurces/Images/Business Simulations/2.jpg");
  }
  66%, 97.5% {
    background-image: url("../Resurces/Images/Business Simulations/3.jpg");
  }
}