Hero Motocorp — Missing problem

Address:

Lucknow, Uttar Pradesh, 226003

MISSING PROBLEM, when i cross the speed of 30 missing is start and increase speed engine is off, HEAD LIGHT when i on light after few minutes its off, MILEAGE PROBLEM
Each n every problem start after service,

In a week visit two time on servicce centre but problem is still on and increase so i humble request to solve my querry. this cause make.