Before you start the game you have to play the thief.
Trying to get to a door in rafters above guards but there is nothing to tell you how.
To do this I guess it a mini game before the game it self starts. Do you know how to
Walk the rafter to get to the door with out alerting the guards.
Where did you get the game?
What you described doesn't sound like anything that happens in Secret Files 2: Puritas Cordis.
Could it be a different game with the same or similar name?
Or maybe a demo with something that doesn't take place in the actual game?
Secret Files 2: Puritas Cordis is a point-and-click.
In a "rafter walking" situation with a point-and-click, you'd probably click in the general direction of the rafters or look for a hotspot there.
With a keyboard-controlled game you'd use the arrow keys or WASD keys to move over the rafters. Secret Files 2: Puritas Cordis was not keyboard-controlled, so if using keyboard controls actually does something, you don't have the game you think you do.
This is how Secret Files 2 is supposed to start
https://www.youtube.com/watch?v=Of9ISrg2uuk