The Apostle Paul wrote four letters to the Corinthians but the Holy Spirit only gave us two in the Bible. These other letters are referenced in the following two passages:
I wrote to you in my letter not to associate with sexually immoral people...
1 Cor 5:9
And I wrote as I did, so that when I came I might not suffer pain from those who should have made me rejoice, for I felt sure of all of you, that my joy would be the joy of you all. For I wrote to you out of much affliction and anguish of heart and with many tears, not to cause you pain but to let you know the abundant love that I have for you.
2 Cor 2:3-4
We do not know why the Holy Spirit only recorded two letters to the Corinthians in the Bible. But we can be supremely confident that the books that are included in the Bible are sufficient and complete.
Now Jesus did many other signs in the presence of the disciples, which are not written in this book; but these are written so that you may believe that Jesus is the Christ, the Son of God, and that by believing you may have life in his name.
When we read the Bible, we are receiving just enough information for us to learn about God and His plan for all humanity. Some people are tempted to add to God’s Word by reading other literary religious works. Some even think there are other prophets or Apostles that should be included. But the Bible was put together by men directed by God through the Holy Spirit. It is infallible and complete.
The Bible is just enough for us to believe that Jesus is the Messiah, the Son of God, and that there is no other name under Heaven or on Earth by whom we can be saved.
Love and trust the Lord; seek His will in your life.