Okay, first things first:
I needed a long time to figure out, how to control both players.
After that I needed to figure out how to actually play the game, until I got to the point of the labyrinth where I (Spoiler ahead)
Had to look to a wall, where there was a plan of the labyrinth (mirrored) where a specific spot was marked. I walked to it with both characters but didn't actually was able to got ahead.
Also, when reloading the game (with escape), you had 3 Players (up to 4 possible I guess)
Also, I was not able to reload the level I was currently on, only the level prior to that, so I had to redo it again.