For your age and height your weight is proper!
I’m gonna be completely honest with you, you cannot reduce body fat in a particular area of the body. It simply doesn’t work that way. You can reduce the total body fat but unfortunately for everyone, the fat around the belly and lower back is the most stubborn out of all! Your body fat will first reduce in your arms and legs, then shoulders,back and chest and ultimately your stomach. So in order to reach there you have to burn fat consistently for a long period of time!
Now the only way you can burn body fat is by remaining in a caloric deficit! What I mean by that is, if you spend2500 calories a day, then you must eat less than 2500 calories like 2300 or somewhere around that number everyday to constantly burn fat.
Here again, nutrition is the most important. Making sure that you remain in a caloric deficit is super important! You can use healthify me, and set goal as weight loss and can track food! It’s a super useful app honestly!
Now when it comes to working out, you are 15 right now and honestly, just playing outside, everyday or going for a jog or playing some sport consistently is good enough. But I do recommend you start lifting weights but slowly, progressing! Studies show that the best way to burn fat is resistance training or weight training! But it’s contravercial since weight training is basically for building muscle but if don’t eat enough you will not build muscle but actually deteriorate them!
What I honestly suggest you to do is not fat loss but actually building muscle! You are very young and your hormones are at it’s peak! Don’t waste it on losing fat! At your age, you will build muscle like a beast! Lift weights, eat a lot, maintain a caloric surplus and you’ll see amazing results!
I do remember a study done on young people showing that you can actually build muscle and lose fat at the same time! So focus on building muscle! You will become bigger and stronger and later if you end up putting a lot of fat, only then consider losing fat! Your priority should be to build muscle!
Hope this helped