Need middle area of grid to scroll normally

Hello! I need urgent help. I’m making my first website for a client and I have an issue implementing my design. So here’s the deal:

My website is basically a grid that takes 100vw and 100 vh of the viewport and is fixed to the body. It has 4 areas of which only 1 needs to scroll normally like any other website. The problem is that I can’t seem to find a way to make that specific area scrollable with the page.

Here is a wireframe of my website and an example of the design so you can see what needs to be done, I think it must be simple but who knows, maybe it’s not. Here we go and thank you so much! Also I left my read-only link below as well!

Here is my site Read-Only: