Ceilings are done approximately the same as walls – drywall attached to studs (in this case, joists) – with openings in them for fixtures (in this case, recessed lights, instead of switches). There's molding to cover the seams.
And it's backbreaking.
Drywall Lift1): a lift used to raise and hold the panel where it's needed, so that it can be attached to joists.Panel Lifter: see drywall lift.Use drywall panels hung from the base of girders (or in between the girders) for most of the ceiling.
Note that if the girders are spaced @ 90cm, panels will have to be cut, taking time and generating waste.