Fixed Nav Bar - scroll back on mobile, fixed on desktop?

Site URL: https://hexahedron-octahedron-trgh.squarespace.com/

PW = lisa

I am using anchor links on a simple continuous. scroll site.

I am having trouble getting the spacing to work correctly on both mobile and desktop. Seems like the scroll back choice works best on mobile, and the fixed works best on the desktop (so when it jumps, it neither covers up nor misses content)

Any thoughts?

Thanks in advance