I need some sound advice on how to deal with heavy mould?

There is still a leak somewhere. It wouldn’t still be wet 5 years later without some sort of leak.
I would get a plumber to stop the leak, then spray it with bleach.
I wouldn’t disturb the mold spores until the insurance company sees it.
Many insurance companies exclude mold damage. You might want to check that out, and maybe gather documentation that the incident happened 5 years ago. The mold exclusion may not have been in place at that time.

@Judi Hi Judi no it happened 8 days ago.

Just want to make sure you know not to mix the vinegar and the bleach

Don’t mess with it get your neighbors insurance company or yours to clean it. Mold can be dangerous Here is Center For Disease Control webpage for mold. If you are allergic it can have a reaction to breathing or contact. Plus your landlord must be notified.

I used to have a big problem on one wall with mold back in my old place.

I’m not sure if you can buy it where you are, but I found some special paint in the hardware store here. A normal tin of paint is about 40 bucks here, this special paint was about 200 for a half size tin, I applied it to the wall and never had any problems with mold for the rest of the time I lived there, a good few years.

I know this is not exactly a solution to your problem, but it is relevant and could maybe be of some help.

Note: I was told that the paint works by trapping the mold in the wall.

Coincidently, my plumber left here ten minutes ago. Not only did he fix a leaky toilet on the first floor but he removed the rotting plaster and wood under the toilet in the floor below. He said to get rid of the mold and mildew and rot asap.

He also said that it would take several weeks to dry out enough to replace everything, including some parts of the polypropylene pipes that are 26 years olf.

So he returns at the end of the month to do the repairs. I am happy to no longer be breathing that crap.

@Tropical_Willie so it is better to not disturb it then?

I want to say, leave it be, because upsetting it may release more spores, but the paint trick sounds like a good idea.

Problem with that is, insurance assessors are going to come and want to see the extent of the damage, so before you do anything, you need to make sure the neighbours know how big a mess they made and how much of your clothing and shoes, etc were ruined. I am not sure if you own your apartments or rent them, but you should probably contact your contents insurance people and find out if you need to make a claim with them and they will try to claim against your neighbours insurance. Not sure how it works there.

You have a rotted wall though no fault of your own and it should fall on the neighbours or landlord to fix it up. Sooner rather than later, because rot spreads fast.

Personally, I am very sensitive to mold. I would have to move to another apartment if anything like that happened to me.

We have had mold form on the back wall of our enclosed patio, and I sprayed it with full strength chlorine. That seemed to solve the issue.

Yes @Shippy, @cazzie is right do not touch it or blow on it.

++ DO NOT DISTURB IT ++ spores will fly all over.

You can spray bleach water on it to kill the spores and keep it from spreading.