What is the gospel of Christ considering I Corinthians 15:11?

The answer is in verses 1-10. For Gentiles, it is merely to believe in Yeshua, turn from paganism and worship the God of Israel and that is all they have to do in order to enter the community. Once there, Sha’ul, in other parts of the letter addresses their issues about how to integrate into the Sect of the Way, a Jewish sect of the First Century (Acts 24:14, ESV)

Sha’ul, in 1 Cor. 15:1–10, shows the progression of the Gospel given by Yeshua Ha Mashiach to the Apostles and then to Sha’ul. The same message through the people designated to be His messengers. Then Sha’ul goes on to talk about the significance of the resurrection. Apparently, there must have been some issues in Corinth about the idea of resurrection. Perhaps there were sects talking to them, perhaps like the Sadducees or others, who did not believe in the resurrection. Always try to understand the text as the first audience did. Why would Sha’ul be writing to THEM about these issues? Were they worried about future believers in the 21st century? Were Paul’s letters intended to be used as Theological textbooks? No! They were worried about their situation in view of the Roman system which their new belief put them at odds with civically and religiously. These Gentiles were wondering how they would fit into Israel. How would their newly found lifestyle impact their standing not only with the Jewish people but also with a very oppressive Rome.