Position sticky

I am having a really hard time wrapping my head around sticky elements. I have created a page and I need to have the left navbar and the header to be sticky. The header is working as expected but the left navbar I cannot figure out. Left navbar needs to be sticky and 100% height. When content inside navbar grows past 100% height inside navbar content needs to scroll. Main page content needs to scroll if longer than 100% height also. If I apply sticky top 10.5vh to navbar_sticky it does not work. If I apply sticky top 10.5vh to navbar_header, it works. I cannot figure this out.

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