I ripped the two usb-ports from the board and soldered both USB ports paralel. So i can drain more amps out of the board, and it works. For over an hour i doesnt see the undervoltage symbol. Everything was plugged in: the printer, a bigger TFT, and a more amps hungry raspi3. I am satisfied.
i also get my 180 degree adapter from ali-express.
USB_adapter