Electric Bike Momentum, Very Soft to ride, need controller

As you can see Bike is really good presentation, very well kept, absolutely clean, always in shed. Rides super confortable and softly. Lights can be turned on/off from throttle display. It has throttle but it doesn't work. It was working fine until one day stopped, mechanic said need new throttle which I changed and nothing, now said needs a new controller as the motor is fine. I don't want to spend more time on it so I will sell it to somebody that knows more about it.