Was the Prophet illiterate, and was he proficient in languages other than Arabic, and were the Gospel and the Torah present in Mecca during his time, and was the knowledge of his people of these books and the Prophet's knowledge of the doctrine of the Trinity considered a miracle?

The Prophet, peace be upon him, was illiterate; he neither read nor wrote. This is a perfection for him and a miracle indicating that the knowledge, wisdom, and the great Book he brought were all from Allah the Almighty. His description as illiterate was mentioned in the Holy Quran. Allah the Almighty says: "And you did not recite before it any scripture, nor did you inscribe it with your right hand. Otherwise, the falsifiers would have had doubt." (Al-Ankabut: 48), and Allah the Almighty says: "Those who follow the Messenger, the unlettered prophet" (Al-A'raf: 157). The Messenger, peace be upon him, did not speak a language other than Arabic, and the people of Mecca were not aware of the contents of the Torah and the Gospel. The Holy Quran also nullified the doctrine of the Trinity, as in His saying, the Almighty: "O People of the Scripture, do not exceed limits in your religion or say about Allah except the truth. The Messiah, Jesus, the son of Mary, was but a messenger of Allah and His word which He directed to Mary and a soul [created at a command] from Him. So believe in Allah and His messengers. And do not say 'three'; desist—it is better for you. Indeed, Allah is but one God." (An-Nisa: 171).