I agree with Josef on everything. I have lost around 16KG throughout half a year, and I'm looking to lose my last few KG's. I still have tons of muscle so if you do it correct you shouldn't have any problem with muscle loss.
Nutrition: Exactly like Josef said, calorie deficit is the KEY to lose fat, it's not eating this, eating that, you can literally eat anything and still lose fat but if you want to be healthy and preserve as much muscle mass (and potentially gain some), you want 80% to 90% of your daily intake to be healthy homemade foods or non-processed foods. Try to drink more than 2 liters of water, possibly 3 if you can. Don't worry too much about protein, carbs and fat intake and all that because you will end up NOT in a calorie deficit - the main ingredient of fat loss. Just try to eat all these healthy foods as much as you can, you know: meats, fish, eggs, milk, vegetables, fruits, etc. Eat till you're full and no more, I know it's tempting to finish the whole plate but if you're already full just give it to your parents if they want to eat or something, don't worry about it too much. Green tea also helps a lot. One thing that will make you lose a lot of muscle is: crash diets - you don't want to eat only 300-1000 calories a day, that's especially bad for a growing teenager. Just stop eating junk foods and all that bad things, you can eat it maybe once a week at first but try to eat it less and less.
Training: You want to have consistent and continuous workouts, both cardio and calisthenics/strength. I slacked off in the past with training but something hit me and I made myself a plan that I've been following for a month and will continue following it. I basically have Full body workouts every second day, and cardio every second rest day if that makes sense:
Monday: Full Body Workout
Tuesday: Rest day
Wednesday: Full Body Workout
Friday: Full Body Workout
And I also sometimes have cardio after my full body workouts if I feel like it, but full body workouts burn a lot of calories as well.
And I will say a few words combining Nutrition and Workout. You might have Chris' nutrition program or calculated your TDEE or DIM (Total Daily Energy Expenditure or Daily Intake Maintenance, which is you BMR multiplied by activity multiplication, which for moderately active is 1.55). Don't make the same mistake I did. I found out my mistake why I wasn't losing fat. Like I said I slacked off with my workouts, and my DIM/TDEE was 2912 calories, but that was if I workout 3-5 times a week, and I was working out like maybe twice a week, sometimes even once a week, so the DIM lowers a lot, and I thought I was eating in a deficit because of the DIM being 2912, I was eating like 2500 calories (I didn't count them though), but my BMR is 1878 calories, and if I workout twice a week, it's gonna be like 2300 or something, so I was maybe eating in a calorie surplus. I found that out and started working out consistently ever since. So don't make the same mistake I did.
Intermittent Fasting: This is the tool that helped me lose over 15KG in half a year, which might not seem like a lot, but knowing my past activity levels and everything, I am proud where I am now. Intermittent fasting is a way of eating, you eat for 8 hours and fast the other 16 hours. It might not be good for ectomorphs, but since you're looking to lose fat, you can try this if you can do it consistently. Remember: IT DOES NOT WORK UNLESS YOU HAVE A CALORIE DEFICIT - Eat less calories than your daily intake or DIM or TDEE (same thing). As far for building muscle, intermittent fasting supposedly raises Growth Hormone when fasting so it might preserve muscle but I don't know if I built muscle with intermittent fasting or if it was from the amazing program by Chris, or both combined.
Anything you have to ask, feel free, I'm willing to talk about this topic. Salute!