:root {
  --header-height: 80px;
}

html, 
body {
  height: 100%;
  overflow: hidden;
  margin: 0;
}

.root-content {
  overflow: auto;
  height: 100%;
}

.root-content > div:first-child {
  height: calc(100vh - var(--header-height));
  overflow-y: auto;
}