Very easy to get this achievement.
If you need to just watch a walkthrough or even a speed run while you are playing the game.
Note that cutscenes do count towards time. This game can be completed in under 3 hours (that includes watching all the cutscenes to get the achievement), however if you have the “watch all cinematics achievement” then you can’t just skip all the cutscenes in the game, doing that will put you at finishing the game in 1 to 2 hours.
Again very easy if you just watch a walkthrough while you play.
(Pausing the game does not count towards time so feel free to pause at anytime to stop the time)