<div class="konusma-balonu">
  İnsan gerçekten hayret ediyor.
</div>

.konusma-balonu{
  background-color:#40DBE5;
  float:left;
  padding:10px 20px;
  border-radius:5px;
  font-size:20px;
  position:relative;
  color: white;
}

.konusma-balonu:after{
  content: '';
  position:absolute;
  right: 30px;
  bottom:-30px;
  border-style: solid;
  border-top-width: 30px;
  border-right-width: 15px;
  border-left-width: 15px;
  border-top-color:  #40DBE5;
  border-right-color:  transparent;
  border-bottom-color:  transparent;
  border-left-color:  transparent;
}