Pectus carnitium can it be fixed by bodybuilding ?!?
Yes, it will help to build up your upper body muscles. My sternum was quite prominent when growing up, was really skinny, and around 17 I started working a lot harder in a job where I was lifting sacks weighing 50 pounds- thousands of them a week. In about 6 weeks I looked totally different, went from 155 pounds, visible ribs and backbone, to about 175, and all new muscle growth. After working there for a year, I was up to about 190, no fat and my once pointy chest was not really noticeable at all. I still have a barrel like chest, but when I was decently buff I was proud to take my shirt off- when I was so skinny i was ashamed to because the chest stuck out so badly. So yes, body building may well help you a lot. And as you mature, you may naturally broaden out anyway but the working out sure should help. Good luck.
How can I increase my arm muscle size (40 centimeters)?
Well your arms are already nearly 16". With that being said they probably won't grow much more Unless you add bodyweight. Obviously the goal is to add muscle, not fat. You can expect to gain about an inch on your arms every 10-20lbs you gain from here on out up to 18-20" arms. After that it will be genetics that determine if you can get them any bigger no matter how much weight you gain.
What is the limiting factor in muscle growth?
The body will only utilize whatever protein is necessary for muscle making. Let's say you're working out for 2 hours straight, but not with enough weight to stress your muscles. Then you don't need extra protein because you're not "building" muscle. You're merely maintaining what you have (and you might already be overeating protein anyway). Let's say that you're working out 30 minutes straight with the heaviest weights you can do 10 reps with before the point of fatigue (which is how body builders train). Then you may need more protein because you're stressing the muscles and ripping them. But again, you may already be eating enough protein as it is. Protein doesn't magically turn into muscle by osmosis.