Kung Fu can be learned at all ages,, the only thing that will be difficult for you is your flexibility which you need to watch after since you've already gone through puberty, the problem is is that Kung Fu is ment to be learned quickly, but people need money and slow down the process to keep yu in training longer and if your as dedicated as you say you are, you wont be able to truly unlock all your potentials learning from these commercialized Kung Fu teachers, if you are really serious you must find a real Kung Fu Sifu/Master, and Kung Fu is ment to be free flowing and perpetual, not many can teach the art properly, fortionatly i have found a true master, and i am 15 i just started, the best thing you can ever do to elevate yourself, good luck,