When first starting open the note on the table and click "Stay in hell" or something idk

Story achievement just get passed the lava

Talk to the knight in the hero camp to the left after the lava

Play the guitar that is next to the Stalker (I think) in the hero camp

Story achievement, open the door after the lava. puzzle is on a path to the right of the door.

code is: 1408 or something I don't entirely remember

Story achievement, collect one item from each room and bring it to the end of the hallway

Pride: Mirror in corner inside drawer
Sloth: hourglass on desk in corner
Envy: Snake inside a pile of boxes
Lust: stuffed rabbits banging on a chair
Greed: statue of a man on a chair on the desk
Wrath: Knife on desk in middle of room
Gluttony: Wooden spoon on top of barrels

Story achievement sneak past the Nazi zombies

tip: Go right almost all the way, hide behind a wall on the far left wait for the zombie to pass before continuing, go to shelves on the right wait for the zombie to pass and walk behind him then turn right to get the bunks or something. follow till you see the small zombie and go left till he turns around and run to where he stopped to turn around and follow that all the way through till you get to the painting and just walk behind

It might be all wrong because I'm not playing it again to conform.

Before going into the portal to end the game, go right and head up the stairs to get to the door jumping puzzle, follow the gray doors all the way and read the note at the end.

Walk into the portal after leaving the nazi base