How to make the same scrolling side menu as on the DTF site?

Question

css

I want to make a side menu, like on this site: https://dtf.ru . How difficult is it and by what means can such a scrolling menu be made (so that its content does not crawl out of the screen and the scrollbar is present from the very beginning)

Answer 1

https://jsfiddle.net/t8ka2mng/
It remains to style the scroll.
You can replace height with max-height.

Answer 2

I tried to hide the slider to scroll with the mouse wheel and this is what happened: