Well… to a large degree, what the “real Jesus” actually said is a pretty big mystery. The earliest Christian writings we have are Paul’s letters, from the 50s AD, and he doesn’t mention any of Jesus teachings (for Paul, Jesus is more of a magical resurrection figure than a philosopher to follow). The earliest gospel, Mark, is probably from around 80 AD, and the others are a little later.
Mark, Matthew, and Luke clearly share some sources, and these sources contain “sayings” of Jesus. So those might be closer to what the real Jesus said, but it’s hard to tell. There’s also the gospel of Thomas, which is more gnosticy. But the problem is that ancient writers (and even ancient historians) were terribly unreliable. Even Thucidydes, widely regarded as the best of all ancient historians, simply made up entire speeches by famous heroic figures. Ancient people did not have anything like our modern idea of objectivity and accuracy in reporting, and there are obvious examples of gospel writers putting things to reflect their sectarian agenda (Matthew’s sermon on the mount is often cited as a smack-down of Paul and his rival sect).
What all the sources in the Bible do agree on, though, is that Jesus was very much against divorce. That’s the one thing we can be pretty sure of.
As for what else the real Jesus “really” said, I think it’s mostly speculation. His cult seems to have absorbed an earlier cult by John the Baptist. I like some of the things Jesus says (the golden rule, nonviolence) but those things had been said before, without the cultishness.