If you want to do repairs on your Derbi Senda XRace 50 SM then it is always a good plan to have access to a Workshop Manual to use as personal reference if you want to know techniques to take off a specific part including Brake Pads and install it again safely.
Derbi Senda XRace 50 SM Workshop Manuals are able to offer identifiable diagnostic wisdom for the car or truck so if something is faulty it will help you determine what the issue is and the way to resolve it. You will be able to evaluate if this can be achieved by yourself or that the job is just too big you can actually make a booking for your Senda XRace 50 SM in with a nearby car garage.
Derbi Senda XRace 50 SM manual