Neither are grammatically correct because the first one is missing an apostrophe between the ‘n’ and ‘t’ in “haven’t”. It also doesn’t make sense for it to say “haven’t didn’t it”. The second one has two haven’t’s in it and it doesn’t make sense for it to say “haven’t haven’t it”. A grammatically correct form would be: “Sometimes I think I’m already dead, but I haven’t died yet.”
