The work we conducted this week was probably the hardest and the least pleasant so far. We had to work in hot weather, using significant heat source (the flaming torch), and carry heavy loads (one roll of roofing felt weights about 30 kgs / 66 lbs).
But now the roof is waterproof and I can finish the work in any weather.
We also added some wooden beams to support the roof, so that the deflection caused by wind or snow load would be smaller. And we sprayed the top side of boards with antifungal protection (the green stuff) so that any moisture remaining in the boards would not cause the fungus to grow.