.column2-wrap{
  display:flex;
  flex-wrap:wrap;
  justify-content:space-between;
}
.column2-inner {
  width:100%;
  margin-top:20px;
}

@media (min-width: 600px) {
  .column2-inner {
    flex-basis:calc((100% - 20px) / 2);
    max-width:calc((100% - 20px) / 2);
    <!--margin-top:20px;-->
  }
}