Ceiling pasterboard issues / Bathroom

Hi!

My bathroom's ceiling has some issues that I need to resolve.
1. Mould. I applied some bleach diluted in water and it's now gone. I'm planning to repaint over it with damp-proof paint. Is that ok?
2. paint flaking. In some parts of the ceiling, the paint is flaking off. Not sure how to repair it? Should I scrap/sandpaper it, and then repaint over?
3. chunks lifting off the plasterboard. I'm not sure what is lifting off, seems to be a thin layer of plaster with paints over it. It is lifting off at on a straight line. It seems to be where the plasterboard is fixed to the metal frame. see attached picture. I have no idea how to repaint this and this is the biggest issue. I'm thinking of removing it as far as I can, then plaster over it and then repaint. Any advice on this?

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Problems in a bathroom with mould, flaking paint etc are all to do with lack of ventilation. An extractor fan is really a must when trying to avoid problems. The bleach will get rid of the mould, and any flaking/loose paint will need to be removed. Only then will you find out whether the ceiling will be suitable to re-paint.
The "chunks of thin plaster lifting off in a straight line" sounds to me as the tape/s are coming away from the plasterboard joints. If it was me, i'd remove "all" the tapes, put on new ones, prep the ceiling, then PVA and skim the whole ceiling. Once the ceiling has been skimmed, let it dry for a day or two, then mist coat/seal the new plaster, then paint it with a "good quality bathroom paint",, but the key to the whole thing is ventilation. Have a word with a couple of reputable local plasterer and get 2 or 3 quotes. It's not a big job, but unless you are capable, plastering a ceiling is not an everyday DIY job.

A mist coat is thinned down MATT EMULSION. It is normally thinned dowm 2/3 rds matt emulsion, to 1/3rd water. Some even go 50/50, half paint, half water.
I prefer 2/3rds,, 1/3rd.
Roller on one or two coats, let it dry, then put on your quality bathroom paint.
Don't forget to install a decent extractor fan, plus open the window a little.

There has been a water leak from upstairs recently, and it could be due to that, at least that's what the contractor told me. I'm waiting for him to come back with a quote.
I have an extractor fan in place, but yes the bathroom get steamy very quickly especially in winter and there isn't a window I can open.
I'm planning to install a heater in the bathroom so at least in winter the bathroom isn't as cold and doesn't get as steamy if you take a hot shower in the morning. Probably will replace the extractor on your advice too. On this, is there any way to trace where the extracted air goes? There are two events outside my balcony but I don't think it's connected (neither if they should...)