unfortunately you cannot change the direction of rotation with Controllino MINI. Digital output internally contains only high side switch connecting the load (motor in your case) to input voltage. If you want to connect the motor and change the rotation direction, use Controllino MEGA, it has Half H-Bridge for such purposes.
Via potentiometer you can regulate the rotation speed, but you will have power looses on this potentiometer when connected in series with the motor. For better control of the speed you can use PWM modulation on the output and use for example potentiometer for MINI analog input and do the regulation in Software (transfer internally voltage information from analog input to PWM digital output.
Also please note, that digital output of the controllino MINI has nominal current of 2A. If you are using motor with 4A, digital output can be switch OFF because of overload.
Have a fine day and thank you for using CONTROLLINO.