One of the things I found very interesting when I translated the Greek text of 1 Corinthians 15:1-5 into English was that there is an interrogative pronoun (tini with the acute accent on the first vowel) in verse 2 that most English translations don't translate, at least not as a question. But the apostle Paul is asking the Corinthians a question about the gospel. He's basically asking them: What have I preached to you? What is the good news I preached to you? Then Paul proceeds to remind the Corinthians (and us today) of what the gospel really is.
What follows is my personal translation of 1 Corinthians 15:1-5 from the Koine Greek New Testament. The Greek text I used is from The Reader's Greek New Testament, 2nd Edition (Grand Rapids: Zondervan, 2007).
A Free Grace translation of 1 Corinthians 15:1-5:
1 Now I declare to you, brothers, the gospel, which I announced as good news to you, which also you received, in which also you stand, 2 through which also you are being saved. For what announcement have I preached to you if you know it? Except if not, you believed to no purpose. 3 For I delivered to you in first order of importance that which also I received: that Christ died for our sins according to the Scriptures, 4 and that He was buried, and that He was raised on the third day according to the Scriptures, 5 and that He was seen by Cephas then by the twelve.