Ok, as i knew then.USB Debugging responsible for ADB communication and not fastboot, both are different and if you want to mess with ADB then you need USB Debugging but for fastboot there's no need.
If you enter fastboot mode with "Power and Volume -" you dont need USB debugging.
But if you want to use "adb reboot bootloader" to enter fastboot mode, turn USB debugging on.
I'm going into fastboot with volume down and power.
In the afternoon i will try again