ᐅ Retrofitting insulation in a wooden ceiling of an attic roof, removing the old insulation

Hello,

I have an end-of-terrace house and want to remove the old insulation in the attic and completely insulate it anew.
The attic is normally accessible via a fixed staircase.
The attic was insulated many years ago (not by me) with insulation that has an aluminum foil coating on one side, which I want to remove. I believe there is no vapor barrier installed.
The attic is covered with wood paneling, which I want to remove entirely. A new roof window and an access hatch for the chimney sweep are to be installed.
The wooden floor is covered with tongue and groove boards.

The two rooms below are newly insulated.

I want to know how to handle the attic insulation above since I cannot connect to the vapor barrier below.
The wooden ceiling below is also insulated from underneath.

I made a sketch.