Third attempt and I got lucid.
The second time I woke up from the beep, I turned it of. I turned it of because I thoguht it might wake up my brother, and I should try another day. I went to sleep and "woke up" in a parking lot.
I immediately knew I was dreaming. I guess the lucid part of the dream had a lenght of 2-3 minutes, but it was awsome! I even induced a tornado