Is there anyone from among mankind currently living in Paradise, and if so, how could the prophets have been in it before the advent of Prophet Muhammad, peace and blessings be upon him, who will be the first to be resurrected?

The souls of the prophets, martyrs, and the righteous are in Paradise, while their bodies are on Earth, except for those whom Allah raised with both their spirit and body, like Jesus (peace be upon him). The first to enter Paradise with both his spirit and body will be Prophet Muhammad (peace be upon him). The Prophet's encounter with the prophets in the heavens was with their embodied spirits, not their physical bodies. Matters of the unseen cannot be grasped by intellect, and one must rely on the texts of revelation concerning them.