1 Corinthians 15:3 (KJV 1900) — 3 For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures;
Paul is saying the gospel he recieved is that Christ died for our sins
This is the gospel he and the apostles preached to the unconverted
1 Corinthians 15:11 (KJV 1900) — 11 Therefore whether it were I or they, so we preach, and so ye believed.
and that is the Gospel the unconverted Corinthians heard and in believing were saved
Paul is saying the gospel he recieved is that Christ died for our sins
This is the gospel he and the apostles preached to the unconverted
1 Corinthians 15:11 (KJV 1900) — 11 Therefore whether it were I or they, so we preach, and so ye believed.
and that is the Gospel the unconverted Corinthians heard and in believing were saved