Progress..

By using the Knotmeter I succeeded in reaching the max speed - around 18 knots, but lowering it to 14 knots I am still running flank..

Hmm, 14 knots sounds like what you'd get running Ahead full. Maybe your key commands got mixed around a bit?

If you have external view enabled, take a dip below the water line and see if both screws are turning. Maybe the game thinks you are still charging batteries.

:)

The props are turning 360 rpms full speed ahead and 385 at flank..

This seems like way to little..

And yes the batteries are fully charged and I am not running silent everything is as it should be - except for a slow boot.. :down: