It goes without saying, but you shouldn't overlook the Jewish roots of Jesus. Too many want to skip right to the juicy bits, when in reality, this Jesus guy wasn't wholly original even in a Jewish context (nevermind how the gospels portray him).

That mentioned, no scholar can conclusively state that the authors of the New Testament borrowed from any particular mythology, and part of the reason for that is that some myths, such as dying and rising gods, are plentiful in the ancient world. (On dying and rising gods, check out Baal, Dionysus, Ra, Persephone, Osiris, Ishtar, Baldr, Quetzalcoatl, and Adonis. See The World's Sixteen Crucified Saviors: Christianity Before Christ for more on this topic as it links to Christianity.) The cult of Mithras was a very popular Persian religion that spread through Roman legionnaires, which Manfred Clauss details well (IMO) in his book. I also enjoyed Glenn Holland's Gods in the Desert as a beginning overview of various Near Eastern mythologies. I can't say it's a good ending point for scholarship, but for an introduction it does the job well enough. John Allegro is a controversial writer, but I think he has some good arguments worth hearing, at least.

I've seen it argued (I believe by Dennis MacDonald in "Homeric Epic and the Gospel of Mark," but I may be mixing that up with a scholarly article - sorry, it's been years ago that I read this argument) that the heroic descent into the underworld is a literary map for Jesus's journey across the Sea of Galilee and back again (Mark 5), where his destination is an earthly allegory for Hades. Obviously The Odyssey is the best known example of this journey, but it exists in Gilgamesh too, and many other narratives. Sisyphus is one of my favorites, though that's Greek too, as is the Herakles example.

The virgin birth myth is almost certainly borrowed from elsewhere because Paul, his earliest authentic writings likely from before 70 AD because he doesn't mention the destruction of the Temple, also doesn't mention the virgin birth when discussing Jesus. It doesn't help that the Gospel of Matthew and the Gospel of Luke have different accounts too. The number of virgin births in the ancient world is exhaustive. I can't tell you just one or two to look at, but Dionysus is usually a good place to start (he doesn't have a virgin birth, but he is born prematurely, so Zeus lets him finish developing in his own body before he is "born again," this time "perfect").

If you have a question about a particular story, that would be helpful in showing you similar stories from the ancient world. I hesitate to say that I can show you its roots, as that can be difficult to show, but I will tell you the borrowed/ coopted tale that sucked me into the history of thought. I'll take you down the same intellectual path that I went down before discovering that I hadn't discovered anything novel. This is long, but please bear with me. I think the journey is worth it.

If you look in the synoptics ( Matthew, Mark, Luke ), there's a story about the Sadducees telling Jesus of a woman whose husband died without children. According to Mosaic law, she marries the brother, who dies without children, and she goes through seven brothers like this. They ask, "At the resurrection, to whom is she married?" Jesus answers, "Don't you know the scriptures? She will be like the angels in heaven and there will be no marriage." I ask you, and see if you can answer this before moving on to my next paragraph, to which scriptures is Jesus referring?

It isn't in the OT. The nearest source material we have that Jesus could be referring to is the Book of Enoch, which tells of the second fall of the angels. It isn't important if he quoted from Enoch so much as believed in the Enochian tradition. Basically, Satan and some angels come to Earth to copulate with human women, and then they get buddy-buddy with the men and teach them "every kind of evil," such as astronomy and mathematics and how to make a mule. Yahweh vows to destroy the angels and their offspring, but Enoch intercedes and Satan pleads that the souls of his children be left on the Earth in order to help him "tempt this evil generation." Yahweh allows this but destroys them bodily in a great flood. This sounds awfully familiar, though, so flip over to Genesis 6. "The Nephilim were on the earth both in those days and afterward." Which days? The days leading up to the flood. How were the Nephilim on the earth afterward unless they 1) were on the boat or 2) lived on spiritually? We know Noah's family is never associated with the Nephilim, and for good reason: Noah's bloodline was pure. That only leaves a spiritual continuation, as spirits who wander the earth. "The sons of God saw that the daughters of mankind were beautiful." Who are the sons of God? If you consult a Protestant commentary, they'll tell you the sons of Seth, but this doesn't really ring true. The Hebrew is beney elohim, the same words used in Job 1-2 for the angels in heaven. So we can fairly state that the "sons of God" must be demigods (elohim, I should note, is a plural, so "sons of gods" is a better translation - in fact, if you check out Genesis 1, you'll find the elohim are the creators, not a single deity, but several/ many, and the elohim show up again at Babel). Well this is all well and good, Jesus referencing a tradition and it possibly being mixed into our flood narrative. What else do we have?

Jude quotes directly from the Book of Enoch 1:9. He also references their destruction. "Just as the angels did." Goosebumps, friend. That gives a new light to go back and look at the Sodom story, but that's for another day. Suffice to say, this Enochian tradition is pervasive in the Christian scriptures, suggesting the authors may have believed in it strongly.

Another group that believed in and preserved the Book of Enoch text were the community living in Qumran. Yep, the Dead Sea Scrolls. The most interesting one of the bunch is The Book of the Giants, which appears on various fragments. There are bits that reference Enoch in here, placing the story before the Flood, but the most interesting name of all is a giant named Gilgamesh. Yes, that Babylonian one-third-divine man with a were-bear as a best friend. There's no Enkidu in the Book of the Giants, but there is a very hairy fellow that Gilgamesh seems to be friendly with. This, in my opinion, ties the Enochian tradition that Jesus references with Babylonian mythology, a position that has been argued for decades by better scholars that me.

I hope this helps get you started while you wait for other historians to answer.

I always hear that the resurrection story was taken from Egyptian mythology and same goes for the virgin Mary.

Even if the idea of resurrection is essential in the egyptian religion, the link is actually unlikely. The idea of resurrection was not monopolized by the egyptians and is well known in the ancient world. Never forget that the new testament was not written in 8-7th century like some early versions of the old one but in a world that had been influenced by the greek speaking hellenistic world for more than 300 years. You should also not neglect that the content of the New testament was made by choice, made in the IInd and IIIrd centuries and made (almost) definitive in the IVth century councils.

I, too have heard of this pretended Jesus-Horus connection that is entirely made up. I have only heard of the idea of a baptism of Horus and his 12 followers only to make a parrallel with Jesus and never heard of any sources, certainly because there are none.

To study those questions you could read "The Homeric Epics and the Gospel of Mark" that study the link with greek culture. and "Does the New Testament Imitate Homer?: Four Cases from the Acts of the Apostles" by Dennis Mc Donald You can also check out the work of Richard Carrier, who argues that the whole gospels were written as an evemeric myth, that is, the story about earthly acts of a divinity. some of his lectures are available: Why the Gospels Are Myth: https://www.youtube.com/watch?v=ILldt2XHZw0 Acts as Historical Fiction: https://www.youtube.com/watch?v=B5MUUP4l6l4

Despite the similarity in 'dying and rising', Jesus' resurrection is different in nature from other dying/rising gods' account. This simple matter is due to the pervasive idea of 'bodily resurrection of men' of certain sects of first century Judaism (such as the Pharisees and the Essenes).

When Jesus 'rose again', the New Testament (NT) does not use the language of a rising deity. It refers, rather, to the Davidic 'son of God' who is raised by God. This is why, the texts speak of 'The Spirit of him who raised Jesus...', or 'God has raised this Jesus to life', or 'God was able even to raise him from the dead'.

These texts are talking about Jesus' resurrection not as a divine being who returns to life, but as a human being raised by God, which now takes on the seat of 'Son of God'. In short, Jesus was raised as a man, of which he was 'the first fruits', with others following at the judgment day (cf. 1 Cor). This is the primary sense of NT when speaking about Jesus' resurrection.

The motif of belief in Jesus' resurrection, therefore, is not in the older Mediterranean mythologies of the dying and rising gods, but rather, in Jewish belief in the general resurrection of the dead. Whether this Jewish belief is a by-product of the pagan belief in dying/rising god is another question.