Mold problem in new kitchen - how to prevent it in the future?

Question to the thread starter: I hope that the refrigerator cabinet at the top (at the back on the wall) is open, so that air can come in through the grills at the bottom and exit at the top, right?

Yes, of course it is like that. Or rather, it WAS like that until all that stuff was taken out again...

A refrigerator produces heat that accumulates behind the fridge. This heat must be dissipated to avoid warming the refrigerator and thus driving up electricity costs. This happens through the ventilation grill you have in the base. Perhaps it would be better to install such a grill additionally at the top of the cabinet to improve air circulation and remove moisture.

How do you imagine the surrounding cabinet of a built-in refrigerator? It is of course completely open at the back and it has (at the back) a gap to the wall so that the waste heat can escape freely upwards at the back. Again, my problem with the mold is not behind the refrigerator but next to it.

yes i know how that looks. However, since you have two exterior walls, the air circulation or the openings for it might be too small? Maybe an additional grille at the top on the side of the plan-right exterior wall is necessary. That was just a thought or an idea. The effort required for it would also be very small.

Without having read everything now, with us the kitchen planner planned a free space between the exterior wall and the refrigerator...

I never noticed it until this post, but it could be a solution for you?

So move the entire row and install a cover panel.

(Photo from an oblique top view of the refrigerator, exterior wall on the left)

@
On the back, the minimum of 5cm is usually always maintained. (Refrigerator back without cooler to the wall.)
Here, the ventilation opening in the base (which is present) is crucial for the energy efficiency of the device.

Without having read everything,

... don't pay attention to my post above ;) Somehow the pictures of the kitchen didn't catch my eye at first glance... so my solution is rubbish... (post above can't be edited...)

Interesting: 1. Now that the refrigerator is in the middle of the room, it consumes much less energy - 0.5 instead of 1 kWh per day. 2. Measured the temperature at different spots on the wall with an infrared thermometer, the corner at the bottom with the main mold infestation is by far the coldest spot at 11°C (everywhere else at least 16°C).