If you want to perform maintenance on your own MZ 125 Sportstar then it is usually recommended to have a Workshop Manual for personal reference if perhaps you need to know how you can take out a particular component like the Clutch and install it again in the correct way.
MZ 125 Sportstar Workshop Manuals will provide you with distinct diagnostic guidelines on your car therefore if something is not working it will help you understand what the situation is and tips on how to resolve it. You can then evaluate if you can do this on your own or if the job is simply too big you could make a booking for your 125 Sportstar into a suitable friendly mechanic.
MZ 125 Sportstar manual