quick notes on an approach to refuting christianity

there are several points that i typically make against Christians that are effective.
one of the firsts is to establish the belief in a Creator, and the need for communication, guidance and revelation from Him.
after this I also address the illegitimacy of the Bibles as an unknown tradition. essentially, there is no clear authority or authorisation of the Bible from God, or His Messengers.
when it comes to the subject of the Messiah, the teachings from him are so essential, as with all Messengers of God, that we have to have a reliable source for that information.
as to the New Testament, and its various editions, we can not conclude that the authors were reliable, inspired by God, or eyewitness disciples of the Messiah. the evidences for this are a broad study that I won't mention here, but this is the general conclusion of the overwhelming majority of the Christian and Bible scholars.

aside to this, 1st CE historians are quite certain to the following of the orthodox practices of the Jews being well established among the followers of the Disciples, with the current theology of the Trinitarian, Pauline movement having various historical revisions throughout, not appearing for centuries -- thus, not clearly from the Messiah.
this Pauline movement grew separately from the movement of the Messiah. eventually that Pauline movement, which ran contrary to that of the Messiah and mainstream Jews of the time, overcame, overwhelmed, and covered-up the following of the Disciples of that time.
this was done primarily by misrepresenting the theology of the Tanakh (Jewish Law, Old Testament) and that of the Messiah, as well as the life of the Messiah, to non-Jews who were ignorant of these things.
similarly, modern Christians are likewise ignorant to the theology of their own book in the Old Testament, and have a distorted perspective of it from the New Testament's primary author, Paul (actually there are several authors claiming to be Paul, some forged and still in the NT).
this distorted perspective primarily revolves aroud a passion narrative of the Messiah (that he would suffer die and resurrect), and with a core doctrine of blood atonement. these Christians are taught that a Jew must understand by the Tanakh that "there is no remission of sins without the shedding of blood", i.e. without a sacrifice there is no forgiveness.
this is not the case.

a Jew actually understands "there is no remission of sins without repentance of the sinner". this is what their Torah teaches: "repentance atones for all sins", and the sacrificial system was in place for unintentional sins & could not atone for intentional sins as it required something greater -- repentance. unintentional sins likewise require repentance in the intention for their remission. the Christians do not understand this beautiful and merciful teaching of forgiveness that has been established since Adam, and that is taught in the Torah and the Qur'an: that repentance atones for all sins. they are mislead by Paul into thinking a horrific lie: that God is perfect, we are imperfect, God needs a perfect sacrifice and does all perfection so will provide a perfect sacrifice and that perfect sacrifice is His son, nauzubillah, allowing Him to be merciful and forgiving through a sacrifice of humiliation, torture, and naked bloodiness.
when they accept this understanding that is in their book, that God offers everlasting life eternal to the soul that turns to Him and repents, and that He will forgive them of all their sins and remember the sins no more, then there is no point for the Messiah to die for anyone, and there is no point for them to reject this clear teaching from God that He is One, the Mighty Forgiver, and offers forgiveness for all sins for our repentance, not a sacrifice. Paul's lies on this are very deliberate and can be demonstrated rather well. Another example of his lies is that the Tanakh teaches "anyone who does not affirm that God's Laws are to be observed and obeyed is accursed", and Paul twists it to "anyone who obeys and observes God's Laws are accursed".

to free us from this curse, Paul says, "the Messiah became a curse for us on the cross, freeing us from the Law and having to sacrifice because of it".
this is something that we know the Disciples taught against -- James' epistle is a response to Paul, calling him a foolish man for this innovated thinking of his. the Disciples continued to do sacrifices after the Messiah, and the Tanakh prophecised the Messiah to do sacrifices in the Temple in the last days (yet to happen) meaning that the sacrificial system has not ended (as Paul alleges). even in the book of Acts, James inquires of Paul about this, and Paul caught red handed does not explain that his theology is "from the Messiah" as he alleges, but rather he engages in the sacrifices that he taught against to hide it during interrogation.
essentially, then, you have the Messiah and the Disciples calling to obedience of God and repentance alone atoning for all sins, even with some historical accounts saying the Disciples went on to teach that the Messiah was not crucified or on the cross -- and you also have the group of Paul and his theology and those accepting it, which would eventually go on even to be an overshadowing influence on the other books of the New Testament that were written after Paul and by unknown authors unfamiliar with the territory of Palestine and Jerusalem (i.e. "Matthew", "Mark", "Luke", and "John").

one of the evidences that I use for this, to show theologically motivated innovations in the New Testament, even into the actions/sayings of the Messiah, is by pointing to Luke 4:4 and Matthew 4:4. christian scholarship today know that Mark was written first, after the teachings of Paul and influenced by him, and then Matthew and Luke copied from Mark. this is why there are so many retellings and contradictory versions of stories in those books. historically this was so problematic that the Bibles were rewritten in churches and the stories "harmonised".
there is not much of an overt deal apparent with Luke 4:4 and Matthew 4:4, however. what is noticable is that the Messiah is allegedly quoting the Tanakh, and that quotation is when he is supposedly saying "it is written, man bread etc". and this occurs occasionally. this word for "written" is specified, in the greek manuscripts, to explicitly refer to a quotation of the Old Testament.
Deuteronomy 8:3 is that quotation, so there is not much of a problem here.

however, if something attributes to the Messiah a clear lie against the Tanakh, then this something is not a reliable source of information about the Tanakh (as it's lying against it) or about the Messiah (as the Messiah would not lie, and it is lying against the Messiah by attributing to him a lie). and one such clear lie is in Luke 24:46, which is that "it is written, the Messiah will suffer and die and on the third day resurrect" -- this is a clear lie, because 1) the wording "the Messiah" is absent from the entire Old Testament, so a sentence containing that phrase can not be written in it; 2) the phrase itself is entirely absent; 3) "written" is not "interpreted"; 4) there is nothing that is even remotely interpretable in this way; 5) it is directly contrary to how the Jewish understanding of the Messiah is, which is that the Messiah can not die before accomplishing his Messianic mission, such as freeing the Jews from captivity.
this is, to me, a smoking gun of fabrication and lies intended for those who can not discern it, and today it is readily discernable with the internet and electronic Bibles.

some relevant images: https://imgur.com/a/SjYyufY

what you have here with the "gospels" is that the narrative itself shows that the "gospel" was something that the Messiah proclaimed, but a literary genre from an opposing culture was established in the name of it, and that genre was about the Messiah -- specifically the passion narrative about the Messiah.

an analogy I would give for a Muslim to understand this, would be if the Quraysh wrote a sirah of the Prophet Muhammad ﷺ when he did hijra to Madinah, and they wrote many lies about him, and then they called this sirah "Qur'an". this is what the New Testament Gospels are. except, the Quraysh would've had some relationship with the Prophet Muhammad ﷺ. the writers of the New Testament did not know the Messiah. Paul, especially, did not know him.

i can go into more on other subjects like the trinity and textual & historical criticism, if you'd like. but these are usually enough for most Christians. there are a couple simple arguments against the trinity that work too that you might like. what I like to emphasize is the clarity and universal simplicity of the mercy and loving forgiveness that God Almighty offers in Islam, and how that is so similar to what is offered in the Tanakh, and how the Christian theology is completely a) incoherent; b) insensible; c) a choice especially irrational in comparison to the theology of Islam.

that is, you have a clear theology, and to choose otherwise is madness.
I could offer the description of a euclidean circle, i.e. every point on the outside is equidistant from the center.

and someone else could propose something "hard-to-describe", "difficult to grasp", "complex" concept like a "many-vertices-circle". but really, they would be proposing a contradictory idea, that could never exist in reality. and for me to hesitate at the clear description of a circle that i innately know, for some "hard-to-describe", "difficult to grasp", "complex" concept, would be an absurd decision.

likewise, they have the Islamic understanding, that the religion of Abraham is to make religion sincerely for God Almighty alone, to worship Him alone without any partners, and that He forgives all sins by His loving provision and merciful justice, for everyone who turns to Him and repents sincerely. He did not leave us neglected or abandoned, but He knows what is best for us, wants what is best for us, and sends us guidance from Messengers.

this is a simple concept that anyone can grasp, and there is simply no good, intellectual, rational reason to reject these clear teachings from God for whatever conjectures and assumptions of hearsay that Christianity offers best to the prejudiced and ignorant.
i also have some more material and arguments here: http://bit.ly/sirahpdf