Contradiction with Acts 9:26-27
This verse mentions Paul going to Jerusalem soon after his conversion and being introduced to the apostles by Barnabas, implying an earlier visit than Galatians 1:18 describes.
Acts 9:26-27: And when Saul was come to Jerusalem, he assayed to join himself to the disciples: but they were all afraid of him, and believed not that he was a disciple.
Contradiction with Acts 22:17-18
Paul recounts a vision in Jerusalem shortly after his conversion, suggesting a visit that seems to precede the three-year timeline in Galatians 1:18.
Acts 22:17-18: And it came to pass, that, when I was come again to Jerusalem, even while I prayed in the temple, I was in a trance;