grid content is overlapping code example

Example: displat grid overlapping columns

article {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  grid-auto-rows: 50px;
  grid-gap: 5px;
}

section:nth-child(1) { grid-column: 1 / 4; grid-row: 1; z-index: 1; }
section:nth-child(2) { grid-column: 3 / 5; grid-row: 1; }
section:nth-child(3) { grid-column: 5 / 7; grid-row: 1; }

@media ( max-width: 500px ) {
   article { grid-template-columns: 100px; justify-content: center; }
   section:nth-child(1) { grid-row: 1 / 4; grid-column: 1; }
   section:nth-child(2) { grid-row: 3 / 5; grid-column: 1; }
   section:nth-child(3) { grid-row: 5 / 7; grid-column: 1; }
}

/* non-essential demo styles */
section:nth-child(1) { background-color: lightgreen; }
section:nth-child(2) { background-color: orange; }
section:nth-child(3) { background-color: aqua; }
section {
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 1.2em;
}