EDIT: after hours of test, trial and error it seems to me, that if I cut the electricity connection after shutting down my computer and wait round about for 5 minutes before turning on again the power, the graphic card is working with windows as the flashed one as RX570 in the device manager.
It's not the best solution for me for a daily use. I am open for every kind of solutions 🙃
EDIT2: as attachement my current EFI folder i am using at the moment. (it's the no_acpi mod version 1.0.5, because that was the working way to use a dualboot with windows at my machine)
EFI.7z