*{
  font-family: Avenir, sans-serif;
  font-size: 1em;
  text-align: center;
  margin: 0px;
  padding: 0px;
  box-sizing: border-box;
}
.conteneur-grid{
  display: grid;
  grid-template-columns: repeat(3,1fr);
  grid-template-rows: repeat(3,minmax(80px,1fr));
  border: 2px solid red;
  background-color: #DDD;
  margin: 10px;
}
.conteneur-grid > div{
  padding: 20px 0px;
  background-color: #ED8;
  border: 1px dashed black;
}
.g1{
    grid-column: 1 / 3;
    grid-row: 1;
}
.g4{
    grid-column: 1;
    grid-row: 2 / 4;
}  
.g5{
    grid-column: 3;
    grid-row: 2 / 4;
}