I am 16 and since 14 i started to feel some days really tired and also affects my performance. i know this is part of growing, but how can i minimize?

Sleep/diet/exercise: Make sure that you are getting 8 hours of sleep each night. Try to do aerobic exercise like walking, biking or swimming for at least 30 minutes 5 days a week. Eat a healthy diet with lots of fresh fruits and vegetables. If you do these things it will give you the best chance for healthy growth and vitality. If the tiredness is severe please consult a doctor for some blood tests.

Hard to say for sure: The average 16 yo will need 9 or more hours of restorative sleep/d with extra when studying hard or practicing a sport. You need a balanced nutrition and exercise.You also need to be well. If you can work on the items above and still feel tired, it is time to get a checkup.