Choose a lower difficulty when starting the game. It turns it from a hopeless immediate struggle for survival into a fun exploration, farming and building game with the occasional pocket of zombies to deal with.
This was more than likely because work started on the game before a completed script was available or any actual filming had taken place. They probably rejigged a few things once they were close to finished with development and had some clips to use.
Most games built using the Godot engine run flawlessly on the Steam Deck. It's much lighter in resource requirements than the likes of Unity or Unreal.
Choose a lower difficulty when starting the game. It turns it from a hopeless immediate struggle for survival into a fun exploration, farming and building game with the occasional pocket of zombies to deal with.