Here Paul says that 'we' HE AND THE OTHER APOSTLES would be false witnesses to say God raised up Christ if Christ was not raised up.
15 Yea, and we are found false witnesses of God; because we have testified of God that he raised up Christ: whom he raised not up, if so be that the dead rise not.
16 For if the dead rise not, then is not Christ raised:
17 And if Christ be not raised, your faith is vain; ye are yet in your sins.
18 Then they also which are fallen asleep in Christ are perished.
19 If in this life only we have hope in Christ, we are of all men most miserable.
20 But now is Christ risen from the dead, and become the firstfruits of them that slept.
21 For since by man came death, by man came also the resurrection of the dead.
22 For as in Adam all die, even so in Christ shall all be made alive.
23 But every man in his own order: Christ the firstfruits; afterward they that are Christ's at his coming.
24 Then cometh the end, when he shall have delivered up the kingdom to God, even the Father; when he shall have put down all rule and all authority and power.
25 For he must reign, till he hath put all enemies under his feet.
26 The last enemy that shall be destroyed is death.
27 For he hath put all things under his feet. But when he saith all things are put under him, it is manifest that he is excepted, which did put all things under him.
28 And when all things shall be subdued unto him, then shall the Son also himself be subject unto him that put all things under him, that God may be all in all.
Paul had just got through saying 'we', as in him and the other Apostles would be found false witnesses if God did not raise up Jesus.
Then Paul explained how Jesus was raised, and he then goes back to if Jesus was not raised. What else shall they (believers) do which are baptized for the dead (Jesus), or even their own dead condition of their bodies when they die.
29 Else what shall they do which are baptized for the dead, if the dead rise not at all? why are they then baptized for the dead?
Paul spoke of those he converted to Christianity, and now he is speaking again about 'we'---the Apostle WITNESSES who are preaching that God raised Jesus.
30 And why stand we in jeopardy every hour?
31 I protest by your rejoicing which I have in Christ Jesus our Lord, I die daily.
32 If after the manner of men I have fought with beasts at Ephesus, what advantageth it me, if the dead rise not? let us eat and drink; for to morrow we die.