<div class="overlay">
        <div class="modal">

body { margin: 0; }
.overlay {
  position: fixed;
  background-color: rgba(0, 0, 0, 0.50);
  width: 100%;
  height: 100%;
  top: 0;
  overflow: auto;
}
.modal {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 382px;
  height: 410px;
  background-color: #FAFAFA;
  padding: 40px 35px 40px 35px;
}