title: Making div scrollable instead of page
body: <p>How I can do somthing like that? The question is not about how to write the full code. The question is about how to make such scroll behaviour</p>
  
  <p><img src="https://i.stack.imgur.com/mbmr7.jpg" alt="Scrolling page"></p>
  
  <p>The upper menu should be fixed. When the menu reaches <code>div2</code>, <strong><code>div2</code> starts to scroll</strong>. When <code>div2</code> is finished, it resumes to normal interaction.</p>