These are my 2 cents: "The character who wrote these notes died right after setting foot on argentinian soil again, the one who sort them out and polish them, me, isn't really me, at least I'm not the same inside of me".

He´s talking about himself the whole time, but he wants to show how much he has changed; that´s why he calls himself "the character". He wrote these notes during his journey and he is revising them now, but he doesn't recognize himself anymore in those words.

Let's try a translation: "The character who wrote those notes died when arrived to argentinian land again, the one who sort them out and polish them, me, is not really me, at least I'm not my same inner self". Good luck :))