This is my understanding of this Chapter...beginning at verse 12
12 But if it is preached that Christ has been raised from the dead, how can some of you say that there is no resurrection of the dead? 13 If there is no resurrection of the dead, then not even Christ has been raised.
I think that point is straight forward
14 And if Christ has not been raised, our preaching is useless and so is your faith. 15 More than that, we are then found to be false witnesses about God, for we have testified about God that he raised Christ from the dead. But he did not raise him if in fact the dead are not raised. 16 For if the dead are not raised, then Christ has not been raised either. 17 And if Christ has not been raised, your faith is futile; you are still in your sins. 18 Then those also who have fallen asleep in Christ are lost. 19 If only for this life we have hope in Christ, we are of all people most to be pitied.
Paul goes on to say that his preaching about salvation and the gospel message is useless if Christ was not raised" and our faith is useless also because there is no hope of eternal life if Christ is not raised...so we remain sinners and un-redeemed. This also means that those who have died in Christ, his followers,are lost because of the belief that Christ is not raised. We if only have hope in him while we live this fleshly life and there is no eternal life, we are to be pitied...
20 But Christ has indeed been raised from the dead, the firstfruits of those who have fallen asleep. 21 For since death came through a man, the resurrection of the dead comes also through a man. 22 For as in Adam all die, so in Christ all will be made alive. 23 But each in turn: Christ, the firstfruits; then, when he comes, those who belong to him. 24 Then the end will come, when he hands over the kingdom to God the Father after he has destroyed all dominion, authority and power. 25 For he must reign until he has put all his enemies under his feet. 26 The last enemy to be destroyed is death. 27 For he “has put everything under his feet.” Now when it says that “everything” has been put under him, it is clear that this does not include God himself, who put everything under Christ. 28 When he has done this, then the Son himself will be made subject to him who put everything under him, so that God may be all in all.
...but Christ has indeed been raised from the dead...