Except that it’s not 2000 years ago anymore. Literally everyone knows about Christianity, hell and Jesus already. You’re not coming with some obscure new secret.
If they don’t believe it’s because they don’t want to, so please do leave them alone.
If they look interested instead, then yes of course help them out.
But going to them first and starting telling them how their soul will burn in hell for eternity is definitely not a nice thing to do to anyone. Nobody asked your opinion there.
If me and my group of 200 people believe that there is an evil invisible monster that will curse the soul of everyone unless they come to our church and listen to our priest once a week, would you like all 200 of them to come to you and tell you the same story all over again and again until you give up and go? No, I don’t think you’d like that.
It’s just a matter of respecting each other faith (or lack of) and personal freedom.
Don’t know about the rest, but the South Korea part is simply complete bs