<div class='first-div'>
  First div
</div>

<div class='second-div'>
  First div
</div>

.first-div {
  background-color: red;
  margin-bottom: 2rem;
  display : inline-block;
  width: 100%;
}

.second-div {
  background-color: green;
  margin-top: 3rem;
}