Few thing to know before you start on Nightmare mode 1-
Nightmare mode is unlocked after beating the game once. 2-
You only get a checkpoint when you beat Act 1 and 2. So when you die, you are send back to the start of the Act 3-
The game doesn't save your checkpoint. So if you quit out or shutdown your box, then you have to start from the beginning again. 4-
Your health and stamina upgrades won't carry over, and they are not here either. So you have to beat it with a max of only 3 Hit points.
Act 1 and 3 is not that bad, it's Act 2 that is the hard part, since it's 11 levels long.
I recommend that you use level select, to practice the parts in Act 2. especially the ones after the sewers.
Some information taken from https://www.xboxachievements.com/game/deadlight-directors-cu...