Make the pop up window wrapper semitransparent background to full windows height

How can I make the pop up window wrapper semitransparent background to full windows height. Now the wrapper’s div background fits only a top part of the window.

https://codesandbox.io/s/tours-test-slick-v1uw96?file=/styles.css

<body>
 <section>
  First section
 </section>
 <section>
  Second section
 </section>
 <section>
  <div class="Pop_up_window_wrapper"> //this background div isn't strached to whole body height
    Pop up window
  </div>
  </section>
</body>