second hand bike

Good evening everyone, we are new to the electric bike scene and have bought an electric bike. Of what type it is we don't know as it's all in Chinese. It had 3 settings of throttle only, pedal assist or off. We bought 3 new batteries for it as it was a bit slow but it hasn't helped all that much. It won't drive of the mark very well and on full throttle you can hold it from moving. It runs out of steam when you get it moving as soon as it goes up hill so you have to pedal and have throttle on to get any assistance. Is there anything we should look for too help it work. Also the last light on the right does not illuminate. Thanks for any help.