Help me with mould/damp issue

[Rolopop1]

I feel a bit ashamed/ embarrassed to ask people this IRL but I’ve realised there is some black mould/damp in my sons bedroom behind 2 cupboards.
can anyone give me a step by step of how to sort it?
wash the black of the wall and repaint?
keep windows open or closed?
more heat in room or less?
honestly have not idea where to start and there is a big or a smell now.

I found that it's caused by high humidity. We have a dehumidifier running at 50-55% during winter when we tend to keep windows closed and keeping the house heated also helps. In summer we open windows more often abd its hot so haven't found it to ge an issue then.

This will be a result of lack of airflow. I guess it’s an external wall? Can you move the wardrobes to an internal wall? If not, they need to be moved slightly away from the wall, increase the temperature in the room and make sure it’s aired well. Perhaps get a dehumidifier in there too.
To get rid of the mould you need a proper mould cleaner.

Def no expert here but I would prob try wash off with dilute bleach or fairy liquid / hot water and see how that goes and / or spray some anti-mould spray, and turn the heating on and let it dry out, only thing is it might change the colour of the walls. I second getting a dehumidifier. They draw a huge amount of water out of the air which will probably really help prevent this going forward.

There's a reason why it's behind cupboards. Airflow.

Move cupboards away from exterior walls, bleach on mould, open windows as much as comfortable.

Don't dry any washing indoors.

Get a dehumidifier.

Don't use bleach, use proper mould cleaner. You can pick it up in all the big supermarkets. Bleach will not kill the mould.
Make sure there is airflow gap between back of wardrobes and walls. Also wipe down windows in the morning to get rid of condensation.

We had this when we moved some bookcases.

Use proper mould remover - we used Polycell 3 in 1, it worked brilliantly - and leave the area open for as long as you can. If you have to put furniture against the wall leave a gap. If possible, rearrange the room - we moved the bookshelves to an internal wall, put some shorter furniture where the mould had been, and left a two-inch gap.

It's probably to do with condensation and lack of airflow, but worth checking water isn't leaking in from somewhere.

And dehumidifiers are brilliant. Wouldn't be without one.