Hello, I want to have the sidebar stable eventhough the main content has lots of listings or listing content

For example, if a user scroll through the page the sidebar should not be scrollable once its reached the end of sidebar which has no further blocks/sections, only the main content should be scrollable.

https://classifieds.demoflynax.com/p...san-francisco/ - stable1.jpg

https://classifieds.demoflynax.com/p...ave-88-65.html - stable2.jpg