Witnessing of Jesus who had died, but is alive

Instead, they had several arguments with him about their own religion and about a certain Jesus who had died but whom Paul kept claiming was alive.
Acts 25:19

1)Rev 1:18 And I was dead, and see, I am living for ever, and I have the keys of death and of Hell.

References
1Rev 1:18 And I was dead, and see, I am living for ever, and I have the keys of death and of Hell.