<div class="wrap">
  <div class="wrap-left">
    <div class="item">1</div>
  </div>
  <div class="wrap-right">
    <div class="item">2</div>
    <div class="item">3</div>
    <div class="item">4</div>
    <div class="item">5</div>
    <div class="item">6</div>
    <div class="item">7</div>
  </div>
</div>

.wrap {
  display: flex;
  gap: 15px;
}
.wrap-left, .wrap-right {
  flex-basis: 0;
  flex-grow: 1;
  display: flex;
  flex-direction: column;
  gap: 15px;
}
.item {
  flex-basis: 0;
  flex-grow: 1;
  background: #444;
  font-size: 20px;
  font-weight: 700;
  line-height: 1;
  color: yellow;
}