D7 to D8/9 Differences

D7: print render($page['help']);

D8/9: {{ page.help }}

D7:

    <?php if($page['sidebar_first']){ ?>
      <div class="sidebar-first">
        <?php print render($page['sidebar_first']); ?>
      </div>
    <?php } ?>

D8/9:

    {% if page.sidebar_first %}
      <div class="sidebar-first">
        {{ page.sidebar_first }}
      </div>
    {% endif %}