General question about spare parts and repair

for the first time Kl sorry, for the new thread, had already rummaged abundantly in the forum also with the, search but unfortunately not really found Plan me to buy a scooter, am also ready time & effort for maintenance, repair and the appropriation of know-how to invest is most likely a ReisSchüssel 50s & 2 tacter at the Zig brandsNames I do not fully look through, read in the ad market e.g. Rex, Kymco (read here should be good) Boatian, flex Tech, be nzou ??? to what extent do scooters generally have identical and suitable parts ??? primarily related to engine, drive & wear parts and how to find out which parts exactly you need, i.e. suitable for your own mill thick thank you in advance for answers