it was said by them that Christopher Hitchens should have watched the theist's earlier debates and been prepared, so I decided not to do that

I urge you to prepare properly. Not only Hitchens but Richard Carrier and several other atheists have been humiliated in debate with him, by their own admission. Winning at all is challenge enough, and would be a great service to the world. Given how much of a blow you would find it to lose having fully prepared, I urge you to to reconsider whether you're self-handicapping.