Understanding Layouts

I'm making a page that looks like the attached image, but I'm having trouble trying to figure out the proper way to setup the code. I want the side navigation to load once when a user first navigates to the url, but afterwards I don't want it to rerender. Right now it seems like the page does a complete re-render as I navigate to other segments of my course. I have a learn/$slug/layout.tsx and layout.index.tsx but I don't think this is the proper way to achieve this.. anyone have a clue?