<div class="container">
  <div class="red-block"></div>
  <div class="blue-block"></div>
  <div class="green-block"></div>
  <div class="other-block"></div>
</div>

.container {
    width: 400px;
    height: 200px;
    border: 1px solid black;
    overflow-y: auto;
    margin: 20px;
    padding: 20px;
  }

  .red-block,
  .blue-block,
  .green-block {
    width: 100px;
    height: 100px;
    margin-right: 20px;
  }

  .red-block {
    background-color: red;
  }

  .blue-block {
    background-color: blue;
    position: sticky;
    top: 10px;
  }

  .green-block {
    background-color: green;
  }

  .other-block {
    height: 500px;
    margin-top: 20px;
    width: 100%;
    background-color: rgb(61, 61, 61);
  }