Galatians 1:18-24

Then after three years, I went up to Jerusalem to get acquainted with Peter and stayed with him fifteen days. I saw none of the other apostles—only James, the Lord's brother. I assure you before God that what I am writing you is no lie. Later I went to Syria and Cilicia. I was personally unknown to the churches of Judea that are in Christ.

(v18-22, NIV)

Paul didn't have much contact with the other apostles. In the last paragraph he made the point about receiving God's gospel. As he began to follow Jesus, he did not have much influence from other Christians. This continues to show that Paul's knowledge and teaching of Jesus could only come directly from God. This is God's gospel and Paul was taught directly by God. Even after three years he only met with Paul and James.

They only heard the report: "The man who formerly persecuted us is now preaching the faith he once tried to destroy." And they praised God because of me.

(v23-24, NIV)

Those who heard and believed of Paul's conversion were amazed. Paul's conversion is incredible. How could a full out persecutor of the church end up being an all out follower of Jesus? It is only by God that this is possible. So, people rejoiced in this. It is only by God and Paul's teaching that he received was only by God. When we learn things we often learn through teaching we receive from others. May it be from a teacher in a classroom, or in a book someone wrote, a lot of what we learn comes from someone else. God is the one who reveals things to us as well.

these things God has revealed to use through the Spirit. For the Spirit searches everything, even the depths of God.

(1 Corinthians 2:10, ESV)

You can keep reading in that passage to learn more. God uses the Holy Spirit to teach and reveal things to us. It is by God and through God that we learn some of the things we learn.