Listing only the things you need to do so as to finish the game & one easter egg:
1) in the bedroom, click "use" on the book on the desk. Then click "use" again (having by now been decided to pry)
2) visit all rooms once (time passes)
3) in the corridor, click "use" on the apartment's exit door. (so that you decide to wait still)
4) in the bedroom, you can now go outside, to the balcony. Go there. (you clear your mind)
5) in the bedroom, you can now click "use" on the diary, and read it.
6) in the bedroom, you can now click "use" on the drawer and open it.
7) in the bedroom, click "look" on the drawing you took out of the drawer.
8) in the living room, click "look" on the antique hanging drawers (you now take the blank paper)
9) in the bedroom, click "look" (i think; "use" will still be about actually taking it) on the drawing you took out. Now you made a copy using your pen and the paper.
10) exit to the corridor. Now time passes again. Important: click at the apartment's exit door (to discover it has been locked all this time).
11) go to the balcony, click "use" on the black night hotspot. (so as to decide you won't throw the drawing there; you have nothing to ensure it falls to the ground and itself is too light).
12) exit to the corridor. Click on the bathroom. You throw the original drawing there. Some scene follows.
13) (optional: go to the kitchen, click on the faucet, leave the room; easter egg about revenge

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14) go to the balcony. Click use on the railing. You go to the other side. Click 'use' on the other apartment there.
15) in the new scene, click "use" on the screen. Scene follows + ending
