What is the wisdom behind the creation of man specifically? And does every person have a purpose that none but he can fulfill, or are humans merely puppets moved by God as He wills?

Do not despair; Allah created you for a great purpose, which is to worship Him and develop the earth. Allah says: (And I did not create the jinn and mankind except to worship Me) [Adh-Dhariyat 51:56]. He tests you to see who is best in deeds. Drive away the whispers of Satan by turning to Allah and striving in His obedience. By struggling against your self in obedience, you will taste the sweetness of communion and intimacy with Allah, and you will move from the bliss of obedience in this world to eternal bliss. Be patient with the harm of people and deal with them for Allah's sake, and know that this world is short and the comfort of the Hereafter is eternal for those who are patient and sincere.