I drink 2 to 3 cups of nescafe / day, I want to know if on the long run it will have negative effect on my health?

Not likely . 2-3 cups of coffee a dayis not know to be harmful. If it is not causing you any anxiety, jitteriness. Gastric discomfort or sleep disturbance then you are ok to continue enjoying it. If you are really concerned then consider mixing decaf from time to time.
Coffee and health. Depends. Some people drink coffee for years without problems. Some people develop intestinal problems or sleep problems or jitters with coffee and need to stop stopping coffee suddenly often results in caffeine withdrawl headaches. If you stop , then do it gradually over several weeks.