Can someone please make a guided for the puzzles?

If anyone knows how to open the box that requires a 4 character password/pin, I'd greatly appreciate it, the game offers no clues for the player, making it incredibly difficult. Searched from the Lower Ground floor to the 5F where the floor breaks away entirely, but nothing at all....

were can i save game?

How do I kill him? I throw the barrel at him and he keeps coming?

dat