תרגום - רוסית-אנגלית - Ушёл в мир живых...

Hi Felicitas,
What is the subject of this line?

Felicitas? Are you there?

yep, I'm here. I'm sorry I just didn't quite get the question.
If you are asking about what is the Russian ariant about - it is based on a game of words: in Russian there's a phrase like "уйти в мир мертвых" = "to go into the world of the dead", that is "to pass away", "to die". I think it is some kind of its opposite

I'm asking about the verb. Is it infinitive or simple past? Is it I/you/he or what?

oh I'm sorry
It's "he"

"Living" (adj.) instead of "alive" should clear it a bit more.
I/you/(s)he are the possible variants.
And the verb is in past simple.

P.S. Sorry for interference

Thanks Siberia, that was really useful