The conversion from 2D to 3D was done scene by scene. In total, it took about 6 days (few hours per day) of manual work. Some scenes (especially the last two) were very troublesome and required a lot of perspective corrections and visual errors.
There are still small visual errors that require a disproportionate amount of time to fix, or are impossible to fix due to the conversion technique and technical possibilities.

Better quality available on YT