what can u recommend me about fitness?

Body weight full body workout followed by Split after a period of 6–12 months. You need to create a strong base first. Do workout under supervision of a trainer n get forms n rhythm right.
Rely on home made food as far as possible during first year n only if u want to prepare for competition later, have whey isolates n other supplements. You are teenager, muscles will be built faster in your case. You may take isolates n other nutritional supplements when you hit a plateau.

Bodyweight exercise are few and after a certain period the body gets adapted to it. It needs more stimulation to build.
Hence my recommendation will be to have a push pull workout routine designed for him. Where he can progressively overload and build muscle sooner VIA https://enrgifitness.com/whats-your-motivation/.
However this is under the assumption that his diet is in place if that is not correct, any amount of excercise will not help build muscle.