Originally Answered: how to lose weight healthily?
First, your BMI (body mass index) is completely normal, so you're not overweight in anyway. Therefore you don't _need_ to lose any weight.
If you want to change your body, get more muscles and basically become more fit - well, then it's different. But you don't need to lose weight per se.
When you want to be/become healthy, you need to eat right and exercise right. If you don't rush the changes it's more likely that they'll become permanent and you can maintain your healthy lifestyle. Take small steps and change your eating habits - don't diet.
Proper nutrition and exercise affect your energy level, your looks and most importantly your health. Not just your physical health, but mental health also. When you're lifestyle's in order you're more energetic and more positive - it's actually tested that exercising has the same effect than an antidepressant drug. So it's far better to get moving than to take pills.
In my experience and knowledge, a balanced and healthy diet includes whole grain products, dairy products, vegetables, fruits and berries, nuts and seeds, fish, water and lean meats. Just to mention a few.
Here's more about healthy eating habits:
About one hour of exercise per day will help you stay healthy and keep the extra pounds away. If you want to gain more strength, you need to do strength exercises also, not just cardio. Stretching is important part of staying capable and healthy.
Here's a helpful site about exercising and gaining strength:
I would also like to point out that you're 15 years old, so don't get too fixated on food and exercising. Enjoy your life, have fun with your friends and start a new hobby if you feel like it.