If you wish to execute maintenance on your own Derbi DRD Edition 50 SM then it is usually recommended to have access to a Workshop Manual to keep just for a guide in case that you need to know the right way to take out a specific component for instance the Brake Discs and match it again in the correct way.
Derbi DRD Edition 50 SM Workshop Manuals provide you with specific diagnostic guidelines for the vehicle so if something is not working it will help you determine what the problem is and how you can resolve it. Then you are able to determine if you can do this yourself or if ever the job is just too big you can actually make a booking for your DRD Edition 50 SM in to a decent garage.
Derbi DRD Edition 50 SM manual