<style>
.grid {
    display: grid;
    grid-template-columns: auto auto;
    height: 100px;
    width: 100px;
}
.test {
    grid-column: 1 / span 2;
    grid-row: 1;
    background: red;
}
.big-child {
    width: 500px;
    height: 100px;
}
</style><div class="grid"><div class="test"><div class="big-child"></div></div></div>