Fix a block in position for a section of a page

Hi,

I'd like to fix this block in position (on desktop only) so that it stays in the same position until you scroll to the end of the text in the block on the left side of the page. In fact this is several blocks layered on top of each other in the image below, but i'd like it to remain visible until you scroll to the end of the left hand column which is longer.

Forgot to add this - this is the URL:

https://flamingo-mauve-t7fb.squarespace.com/laiva-gold-equity-1