If the
BMS is damaged, then you should be able to find a suitable
BMS to replace it with, but you will need to provide more details of the battery to determine which
BMS would be suitable.
It looks like your bike has MPIII motors, as shown in Gary's video. They are not MPII motors and, if they are 5 years old, they are too old to be MP4 motors
(with the Sine Wave controllers) as the MP4 was only released in 2014.
If the motors used to make an obvious noise when under load, then they will definitely be the MPIII motors with the older square wave controllers.
Unfortunately you cannot upgrade to a quieter Sine Wave controller.
The MPIII and MP4 motors are different and the controllers are not interchangeable.
Alan