<div class="tooltip">
  <div class="tooltip__arrow"></div>
</div>

body {
  background: #efefef;
}

.tooltip {
  height: 200px;
  width: 300px;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  background: white;
  box-shadow: 0px 5px 15px 0px rgba(0,0,0,0.3);
  
  &__arrow {
    width: 50px;
    height: 25px;
    position: absolute;
    top: 100%;
    left: 50%;
    transform: translateX(-50%);
    overflow: hidden;
    
    &::after {
     content: "";
     position: absolute;
     width: 20px;
     height: 20px;
     background: white;
     transform: translateX(-50%) translateY(-50%) rotate(45deg);
     top: 0;
     left: 50%;
     box-shadow: 1px 1px 20px 0px rgba(0,0,0,0.6);
    }
  }
}