@nycdad,
It's safe to assume that much of what we know as the words of Jesus were written by others after his death. Some were "edits" and some were deliberately included to reflect emerging doctrines. Even so, it's likely that maybe a third of the words attributed to Jesus are original and maybe another third are closely related to things he may have said.
There are ways used by biblical scholars for assessing the probability that an entry is authentic:
Orality: According to current estimates, the gospels weren't written until decades after Jesus' death. Parables, aphorisms, and stories were passed down orally (30 – 50 CE). Biblical researchers judge whether a saying is a short, catchy pericope that could possibly survive intact from the speaker's death until decades later when it was first written down. If so, it's more likely to be authentic. For example, "turn the other cheek".
Irony: Based on several important narrative parables (such as the Parable of the Good Samaritan), biblical scholars assume that irony, reversal, and frustration of expectations were characteristic of Jesus' style. Does a selection present opposites or impossibilities? If it does, it's more likely to be authentic. For example, "love your enemies".
Trust in God: A long discourse attested in three gospels has Jesus telling his listeners not to fret but to trust in the Father. Biblical scholars look for this theme in other sayings they deem authentic. For example, "Ask – it'll be given to you".
Generally, it doesn't really matter. Take what you like from the old book and ignore the stuff you disagree with or don't understand.