<div class="grid">
  <div class="grid__item card1">Card1</div>
  <div class="grid__item card2">Card2</div>
  <div class="grid__item card3">Card3</div>
  <div class="grid__item card4">Card4</div>
  <div class="grid__item card5">Card5</div>
</div>

.grid {
	display: grid;
	grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 30px;
	background: #eee;
}

.card1,
.card2,
.card3,
.card4,
.card5 {
  width: 100%;
  height: 300px;
  box-shadow: 0 0 3px rgba(0,0,0,0.16);
  background: #fff;
  border-radius: 5px;
}