How to make a fixed vertical menu?

Question

css

there is some code like this:

<div class="container">
    <div class="row">
        <div class="col-4">
            <nav>
                тут меню
            </nav>
        </div>
        <div class="col-8">
            тут контент
        </div>
    </div>
</div>

using bootstrap-4. how to fix the side menu in the visibility zone when scrolling, while on the left it should be pressed not to the edge of the screen, but to the edge of the parent col-4?

Answer 1

Demo has it all.