There were 3 fans in the kit.
Two with a "che fy" label with 7000 R/Min and one without label with 5000 R/Min.
From the outside, they are identical.
The 7000 is also very noisy.
The revolutions I measured with a measuring instrument.
The higher speed would also explain the strong cooling.
I have a 80 ohm resistor in series.
The extruder is still sufficiently cooled, the maximum temperature of the nozzle now reaches 230 degrees, the volume is pleasant.
The problem is so that solved for me.