At this point, you seem to be saying "coming back from the dead is impossible, therefore it didn't happen". I think that's the wrong mindset. I think it's more correct to say, "coming back from the dead is impossible, but did it happen?"
See, if God exists, if He's really there, how would we know? Well, a historical instance of the impossible happening might be pretty good evidence that He's actually there. And the resurrection of Jesus is the big, flashing neon sign that says "Look over here. God actually did something."
So the question is, how good is the evidence for the resurrection? Well, there's an account of him appearing in a roomful of his followers (who at that time didn't believe in his resurrection), telling one of them "Look, here's the holes from the nails from when they crucified me. You can stick your finger in them. It's really me." This was written down for us by a guy who was in the room when it happened. That's... pretty good evidence.
To not believe it, you have to believe that it wasn't written by who it says it was, or that he lied about what happened, or that he was mistaken.
If you think the evidence indicates that one of those options is true, fine. But I suspect it's more likely that your position is really going to boil down to "God doesn't exist, therefore the resurrection didn't happen, therefore the story has to be mistaken." That is, your presupposition is determining how you view the evidence. I think it's more rational to give the evidence an honest look, even if the conclusions destroy your presupposition.