Most timelines place the time of Moses around 1350-1450 BC.
So this article is implying that Moses didn’t write the Torah - aka the first five books. Then they are denying Christ, who quoted Moses’ writings often.
No, they are not denying that Moses really spoke those words. The four evangelists, quoted from the Old Testament according to whom they were teaching.
Matthew probably quotes the most in his Gospel, as Christ refers to the older texts. Remember that Christ was trying to convert the Israelites first. Mark doesn’t have quite so many Old Testament quotes, but they are still there.
Because Luke traveled with Paul, his Gospel is more historical for the upbringing and education of the Gentiles. He covers a lot of Christ’s stories in a different tone.
And lastly, John, with his dissertation on the Bread of Life has a totally different focus in some of his writings.
As to when the Old Testament was actually written down, I have been told by a priest that they probably did this when they were in exile in Babylon. Stories had been handed down person to person and family to family until that time.
Does this make sense or is it even more confusing? Check out some of the Bible links I posted, too. They have lots of information on the who, when, where, why and how of the Bible.