Debating with the Jews and Christians about their beliefs and religion
Question

                Because we are studying in America, sometimes we get involved in discussing issues having to do with the Christian and Jewish religions. Is it permissible for us to discuss them?.
Praise be to Allah.Yes, it is permissible for you to speak about that according to what you know, but it is not permissible to speak about that or anything else without knowledge. It is well known that the laws of the Torah and Gospel are among the laws that Allah revealed to His Messengers in ways that were appropriate to their people at those times and in those circumstances. Allah is the Most Wise and All Knowing in all that He legislated and decreed, as He, may He be glorified, says (interpretation of the meaning): “To each among you, We have prescribed a law and a clear way” [al-Maa’idah 5:48].  That was after mentioning His sending down of the Torah and Gospel and Qur'aan in Soorat al-Maa’idah. And Allah says (interpretation of the meaning): “Certainly your Lord is All‑Wise, All‑Knowing” [al-An’am 6:83]. Then the Jews and Christians distorted and altered and introduced into their laws things that were not part of them. Then Allah sent His Prophet Muhammad (blessings and peace of Allah be upon him) with a universal message to all the inhabitants of Earth, both jinn and mankind, and He prescribed for him a universal law, thus abrogating the law of the Torah and Gospel, and He enjoined all the inhabitants of Earth to refer for judgement to the law with which Allah sent Muhammad (blessings and peace of Allah be upon him) and to adopt it to the exclusion of all others, as He said, addressing His Prophet (blessings and peace of Allah be upon him) in Soorah al-Maa’idah (interpretation of the meaning):
“And We have sent down to you (O Muhammad صلى الله عليه وسلم) the Book (this Qur’aan) in truth, confirming the Scripture that came before it and Muhaymin (trustworthy in highness and a witness) over it (old Scriptures). So judge among them by what Allaah has revealed, and follow not their vain desires, diverging away from the truth that has come to you. To each among you, We have prescribed a law and a clear way”
[al-Maa’idah 5:48].
And He said (interpretation of the meaning):
“But no, by your Lord, they can have no Faith, until they make you (O Muhammad صلى الله عليه وسلم) judge in all disputes between them, and find in themselves no resistance against your decisions, and accept (them) with full submission”
[al-Nisa’ 4:65]
“Do they then seek the judgement of (the days of) Ignorance? And who is better in judgement than Allaah for a people who have firm Faith”
[al-Maa’idah 5:50]. 
And there are many similar verses. The one who studies the Holy Qur'aan and reads it a great deal for the purpose of learning and acting upon it, Allah will guide him to the right path, as He says (interpretation of the meaning):
“Verily, this Qur’aan guides to that which is most just and right”
[al-Isra’ 17:9].