I would like to align items one after the other in two columns (like wallapop).
Here it's the best I have achieved (not what I want):
Here it's a code I've build with JSfiddle so you can edit it: https://jsfiddle.net/52qdnLcg/
.parent {
  background-color: #ccc;
}
.child {
  width: 44%;
  background-color: #3c434f;
  margin: 2%;
  display: inline-block;
  text-align: center;
  color: #fff;
}<div class="parent">
  <div class="child" style="height: 150px;">
    1
  </div>
  <div class="child" style="height: 60px;">
    2
  </div>
  <div class="child" style="height: 40px;">
    3
  </div>
  <div class="child" style="height: 70px;">
    4
  </div>
  <div class="child" style="height: 30px;">
    5
  </div>
</div>Thanks in advance!

 
    