sorry for my absence.
Actually the issue is a windows topic. During the first connections I was working with the laptop on external power and in "high performance mode". During my attempts where I was unable to get a connection to the brain I was working on battery in "balanced mode".
So the solution the brainfpv support guy supposed was:
"Can you try switching windows to the "high performance profile". If this doesn't help, use the device manager and try uninstalling the driver that was associated with the Brain and reboot".
However, I solved the issue before I had the answer by simply uninstalling all usb devices below the "usb controller" tab in the devic manager, then directly rebooting the laptop. That worked .... just connected the brainfpv as if there was never a problem .
I didn't have any issues with connections since then, no matter which power profile was activated.