So then Paul was lying when he wrote that the Gospel he preaches is the Gospel that he received from none other than Jesus Christ himself:
"I certify you, brethren, that the gospel which was preached of me is not after man. For I neither received it of man, neither was I taught it, but by the revelation of Jesus Christ."[Galatians 1:11-12]
So is Paul lying??? How come all the other apostles and disciples of his day don't feel the way that you do??? Were they all wrong too???
I will give you a two-fold answer.
One, the Church does not find what St. Paul preached to be at odds with th Gospels. The Church interpretation is in harmony with the Gospels. +Paul is interpretd through the Gospels, as the Old testament is interpreted through the New Testament. Everything is harmonized. But this hamrony did not come about naturally.
Two, historically, +Peter +James, on one side, and +Paul on the other, very very much at odss with each other. The book of Acts (written after both Apostles were dead) tries to smooth things over in that respect. Even later than that, the book of 1 Peter appeared. Written towards the end of the century, it tries to mend the rift between the followers of +Peter and those of +Paul.
1 Peter was specifically written to mend those disagreements, and bring the followers of +Peter (and +james) and those +Paul into one fold. The rift between +Peter and +Paul was significant and serious.