Ill lay it out for you because I believe your heart is in the right place.
Try the bodyweight exercises idea for a while. Even if you still want to lift, do some pushups and bodyweight squats on your off days, it will help develop strength that you are really lacking.
What I told you to do is as simple as it gets.
Day 1
1Bench press(3x10, 3x8, 4x6, or 5x5 just dont go lower than 5 reps for the time being as your form and strength are not advanced enough to handle it)
2 Assistance chest work exercise…probably dips or weighted dips but also incline, or decline barbell or dumbell bench
3Some type of overhead press(push press, military press same idea on the rep schemes)
4Tricep exercise - dumbell or barbell skullcrushers, pushdowns whatever
Day 2
1Barbell Squat (see rep schemes from bench but extra couple of sets are ok)
2Split squat, Leg press or hack squat - higher reps - 8 to 15
3leg curl or glute-ham-raise
4some type of abdominal training
Day 3
1Deadlift (any of the previously mentioned rep schemes are good …possibly even sets of 12 to reinforce good form)
2Barbell or dumbell bent over rows
3chin ups or weighted chins
4shrugs or farmers walk with dumbells
5 some type of curls if you really have to but not really needed
Thats it. As you are just starting out,
you dont need mini-band flying one-arm pushups on a balance ball. Work this basic stuff for as long as it keeps putting on size and strength. Most guys I know that got strong and big started their training with something similar to what I laid out. Stick with this basic stuff, only alternating rep schemes on the 3 powerlifts every couple of weeks. Some will say there is not enough variety but that is not true. If you are eating properly, not doing much of this damned cardio you insist on, and resting well,
you will put on muscle and get strong quick.
Make sure up the weight as often as your form will allow and, most importantly, try to get someone to help you with your form on the basic exercises.
Stop overthinking this and dont throw yourself into some wild Spartan-like regime. You’ll burn out quick and get pissed off. Then you’ll quit. Prof. X just told you this, so listen to him. You have a long road ahead, but at 15 years old, the good news is you have all the time in the world to work on it.
By the way, what about some type of athletic pursuit? Guys your age should be doing something to develop discipline and general athletic ability. Wrestling or some type of martial art are great. If all you do is jog and swim, all you’ll get is weak, slow and uncoordinated. Thats no way for a man to go through life.
Enough silliness. Shovel down your food, crank your iron, no more pictures
until youve done 3 or 4 years of work and listen to what the guys who have been there are telling you.