Today i found this thing:
When i use nornally, the USB-C only works for charging.
But
When i power on the tablet when the usb-C keyboard is plugged in, the usb-C only works with the otg. You can’t charge the tablet until you turn off.
I think this is just a driver issue but i don’t know.
Oh. Same in bios.
Then maybe it is a bios setting for this.