Hi, I'm a 15 year old girl, I weigh 136 pounds and I'm 5'4, my BMi is 21-22 . I know, I'm not even close to being overweight, but I want to lose 5-10 pounds, nothing big really.
Anyway, will I lose weight I leave about 20% of food during each main meal, eat lots of veggies and fruits, stop eating all kinds of sweets, sodas , candy and anything with lots of sugar, never eat junk food, and walk 4-5 days a week for about 1-3 hours? :)


Also, I'm not on any kind of diet or anything and I've been doing this for a week:)

Yes, but you'd be better off talking to a professional nutritionist.

Everything you said except for the very first one. You need those healthy meals 3 times a day. If they include potatoes, pasta, or bread, cut those down about 50%, but keep rice (no Minute rice).
Walking is of course good, but speeding up your heart/pulse is how you really burn calories. Speed walking looks funny, but try it. Carry small weights in each hand.
How about neighborhood jobs walking dogs?

The other thing you need to consider is that you will be exercising which can cause a little muscle mass to build up. This might cover some of the weight loss in the beginning. Cutting out the simple sugars like you had mentioned is a good thing. Just doing a straight 20% drop in portion size won't do anything and could put your body in a starvation mode. Which will cause you to gain weight. Keep a healthy diet and ramp up your exercise. It might take a few weeks to see any weight off, but you will notice some fat disappear.

Healthy eating is important at your age. The issue is you are growing and have to have proper food. If you do not eat proper it can cause growth issues.

If you are not over weight, you need to just control.