A person may speak as many languages as he or she has learned. Whether or not the languages are spoken well, however, is an entirely different story. Assuming a person learns at a rate of 1 language every ~2 years (enough to have a general understanding and be able to hold a basic conversation), this person would be able to learn ~30 languages by age 60. It would be a confusing way to live, but it is entirely possible.

as his/her ability and power .....................................

Scientifically speaking, we use only 20% of our brain faculties ... From this principle, humans may learn all the languages of the world! Should yet they live long enough to learn them all.. :-)