I am trying to build a drop-down menu in a navbar. I have done this, but the list of items is too long to fit on the page (the bottom of the list is hidden) so I therefore need to make the list scrollable. As of now, when the menu is "open" and I scroll, it scrolls the page behind the menu rather than the menu. Please help me figure this out! Below I have posted a bit of my HTML and CSS as it pertains to this drop down menu.
<li class="nav-item dropdown">
<a href="#" class="nav-link dropdown-toggle scrollable-menu" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">INSTRUMENTS</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
{% for instrument in instruments %}
<a href="{% url 'instruments:individual_display' instrument.id %}" class="dropdown-item"> {{ instrument.name }} </a>
{% endfor %}
</div>
</li>
.scrollable-menu {
height: auto;
max-height: 500px;
overflow-x: hidden;
}