Consegui resolver da seguinte forma:
.grid-container {
display: grid;
grid-template-columns: 1fr 1fr 1fr;
grid-gap: 10px;
}
.item3 {
background: #84EEC1;
color: #041833;
grid-row: 1/3;
grid-column: 3/4;
}
.item4 {
grid-row: 2/3;
grid-column: 1/3
}
.item5 {
grid-row: 3/4;
grid-column: 1/3;
}