How can I make the fixed block start its magic action after a certain block using?

Question

css

If the menu block is given position fixed, then it will follow the user when scrolling.
But the menu block is located approximately slightly above the middle of the site, respectively, it is necessary that this block starts its pursuit only from this place.

Please tell me how this can be done?

Answer 1

fixed nails the block to the viewport, sticky was advised above

Answer 2

Google floating menu js