If you have to execute maintenance for your MZ 125 SM Blizzard then it is always a good idea to have access to a Workshop Manual to use as a guide if perhaps you want to know tips to strip off a specific part for instance the Gearbox and install it again successfully.
MZ 125 SM Blizzard Workshop Manuals will give you specified diagnostic guides on your vehicle so if something is broken it can help you find out what the issue is and the way to correct it. You can then analyse if this can be done by yourself or if the job is just too big you can actually book your 125 SM Blizzard in to a suitable garage.
MZ 125 SM Blizzard manual