The Apostles and leaders in the early church were human and did not always agree among themselves on everything.
Peter was used in
Acts 10 (approximately AD 38) to bring the Word to Gentiles.
He was condemned by the Apostle James and other elders for "eating with Gentiles" (an oral law, not a written law).
Later Peter fellowshipped with Gentiles at Antioch but withdrew his fellowship because of his fear of some from the Jerusalem church. This is referenced in
Galatians 2:11-13. Paul probably wrote Galatians in th summer of AD 53 and the incident with Peter was some time before the Jerusalem conference in
Acts 15 which happened in AD 49/50. Barnabas also got carried away in withdrawing from Gentiles. Later Peter refers to Paul's writings as Scripture (
2 Peter 3:15-16). I don't know when Peter wrote his second epistle but it had to be some time before his death which is thought to be in AD 68. When Paul went to Jerusalem in Acts chapter 21 (which would have been in the spring of AD 57) he participated in sacrifices in the Jewish temple per the Apostle James' advice. We are told that there were many Jewish Christians (the Greek word is muriades or ten thousands) who were zealous of the law.
From what I understand, there was diversity among the churches and preachers in that first century just like there is now. They agreed on basics like the Messiahship of Jesus and His resurrection but each local church and each preacher would be affected by his surroundings and background.