.youtube {
  position: relative;
  width: 80%;
  padding-top: 56.25%;
}
.youtube iframe {
  position: absolute;
  top: 0;
  right: 0;
  width: 80%;
  height: 80%;
}
 @media screen and (max-width: 767px) {

.youtube {
  position: relative;
  width: 100%;
  padding-top: 56.25%;
}
.youtube iframe {
  position: absolute;
  top: 0;
  right: 0;
  width: 100%;
  height: 100%;
}
 }