We know that Luke copied from Mark's gospel and from other sources.
Luke tells you this in Luke's introduction.
Luke 1:3
It seemed fitting for me as well,
having investigated everything carefully from the beginning, to write it out for you
in consecutive order.
Luke is not writing about a revelation he received from Jesus.
Luke is merely investigating material he had access to and one of those sources was Mark's gospel.
Luke corrects the rough Greek in Mark's gospel and expands with information from other sources.
In places, the three so called 'synoptic gospels' are similar but not in other places.
Here is a problem for you to solve.
Matthew 28:18-19
And Jesus came up and spoke to them, saying, “All authority has been given to Me in heaven and on earth.
Go therefore and make disciples of all the nations.
If that was what Jesus told the apostles then why do we have the following.
Acts 10:13-14.
A voice came to him, “Get up, Peter, kill and eat!” But Peter said, “By no means, Lord, for I have never eaten anything
unholy and unclean. Again a voice came to him a second time, “What God has cleansed, no longer consider unholy.”
This is before Peter is called to visit the unclean, unholy, Gentile, Cornelius to which Peter replies.
Acts 10:28
And he said to them, “You yourselves know how unlawful it is for a man who is a Jew to associate with a foreigner
or to visit him; and yet God has shown me that I should not call any man unholy or unclean."
Surely Peter remembers what Jesus said "Go therefore and make disciples of all the nations" in Matthew's gospel.
Apparently not.