Root OP5 sideload error: device '(null)' not found

[majorRyan]

Hallo there,
Iam currently trying to unroot my OP5 while facing an issue.
I have already flashed the stock recovery and now in the recovery mode iam not able to install my update
from ADB cuz it gives me the following error "error: device '(null)' not found"

So it seems i have to update the USB driver on that phone and there are a lot of solutions to do that on
the internet like this one

So in the device manager my phone is shown as "unkown device" and when i then try to update the driver by choosing "search for drivers on the computer" /"choose from list of available drivers on my computer"
it doesnt give me the option to choose "Android devices" i have already installed some ADB drivers hoping it to be working then but it didn't.

I have no idea what to to next, so i need ur help.