Detach Shock Nova mirror cabinet

I want to uninstall the shock medicine cabinet. The rather old piece is hanging very tightly. Who knows how to loosen the fitting shown in the picture? I have two of these fittings, each at the top corners. Which screw first?

Unscrew the slotted screw at the front, then it will come loose from the wall.

Unscrew the slotted screw in the front, then it will come loose from the wall.

Possibly the lower slotted screw secures the front one against unscrewing, start with the lower one.
The front slotted screw fastens the cabinet to a hook in the wall, that's why the cabinet is so "rock solid." Nice concept.

That can also be the case, I thought it was for height adjustment.

Cool, many thanks for the help. On Wednesday, we will take action (the two of us!) and we hope that [Ideal Standard] stays intact... I will report back :)

That could be true, I thought it was for height adjustment.

I would say the same: that is just the compensation for the height. I can imagine that it is hooked in, so just push it straight up on the wall (try).