Hello, I made a video for all the achievements. I speak German but you don't need to hear my voice to follow the video. You can mute me or just activate the translator.
At the back of the school building, you have the opportunity to climb a pipe up to the roof. After you are on the roof, you simply have to run to a special point to trigger a conversation. In my video, I show you the exact path.
06:33 Soliloquy