I HAVE GEAR OIL LEAKING Yamaha rx 100 ....100 cc 2 stroke IN THE BOTTOM OF GEAR LIVER, ?

i already replaced the gear shaft,spocket,oil seals,pls help me to avoid this pblmsI HAVE GEAR OIL LEAKING Yamaha rx 100 ....100 cc 2 stroke IN THE BOTTOM OF GEAR LIVER, ?
Take the bike to a repair shop.