I'm afraid to eat what i want because i think i'll gain weight. i'm a 16 year old teenager and everyone tells me it's fine to do. is that true?

Diet & exercise : healthy diet without any ado especially at your age: avoid junk/fast food as much as you can, half of your plate would be vegetables/ fruits, fresh air, sleep well and exercise, good luck

Check out my plate: myplate.gov can guide you in making healthy choices and having a well balanced diet. At 16 you are likely physically active and have some growing left so you have significant caloric and nutrient requirements. Do not be afraid to eat well.