Apostle Paul was a revealer of God’s word and not a theologian as some people thought but most of his messages were the basis for theology and doctrine in churches today. Most of the things done during the Holy Communion came from Paul’s messages. He used so many philosophical terms in his letters to the church (Acts 17:28). Many people had problems with his messages even while he was alive; they find it difficult and interpreted them to their own destruction as Peter said in 2 Peter 3:16.
15 and consider that the longsuffering of our Lord is salvation—as also our beloved brother Paul, according to the wisdom given to him, has written to you,
16 as also in all his epistles, speaking in them of these things, in which are some things hard to understand, which untaught and unstable people twist to their own destruction, as they do also the rest of the Scriptures. (2 Peter 3:15-16)
He had all the education essential for the service God needed him for. Although it was not his intention to serve God, yet he was found by God when there was a need to take Christianity beyond the border of Israel. God made him an instrument who eventually bear His name before the Gentiles, kings and the sons of Israel (Act 9:15). He was used by God to give structure and understanding of HIS message on earth. A faithful man indeed, whenever he gives personal advice, he makes people understand that in his letters but when he receives from the Lord, he also made it clear in his letters (1 Corinthians 7: 6, 10 and 28). He suffered pains, faced persecution and trials all for the sake of the gospel.
Apostles Paul wrote more than the other Apostles. Among the Twenty seven letters which are also called Epistles, thirteen were credited to him; these are Romans, first and Second Corinthians, Galatians, Ephesians, Philippians, Colossians, first and second Thessalonians, first and second Timothy, Titus, and Philemon where he taught about salvation, resurrection, marriage, divorce, end time among others. Many New Testament scholars and students of the scriptures have scrutinized his letters and concluded that he has written more than thirteen letters which were lost and not made available for us today. Some of these lost epistles ( letters ) are referenced to 1 Corinthians 5:9, 2 Corinthians 2:4, 2 Corinthians 7:8-9, Ephesians 3:3 and Colossians 4:16. The letter he wrote to the church of Laodicea (Colossians 4:16) which was to be exchanged with the letter written to the brethren in Colossian is not available for us today. Moreover, you need to know that 1 Thessalonians was the first letter written by Apostle Paul but because the bible was not presented chronologically but theologically, it became number seven.