body {
  background-image: url("https://files.catbox.moe/w6l0uy.png");
  background-repeat: repeat;
}
.box {
  max-width: 1000px;
  margin: 100px auto;
  display: grid;
  grid-gap: 16px;
  grid-template-columns: 300px minmax(0, 1fr);
}
header, nav, main, footer {
  border: black 2px solid;
  padding: 5px;
  border-radius: 10px;
}

header {
  grid-row: 1 / 2;
  grid-column: 1 / 3;
}

nav {
  grid-row: 2 / 3;
  grid-column: 1 / 2;
  height: max-content;
}

main {
  grid-row: 2 / 3;
  grid-column: 2 / 3;
  height: max-content;
}

footer {
  grid-row: 3 / 4;
  grid-column: 1 / 3;
}