Portal: Forbidden Testing Tracks - Episode 3 - Gun Juggling

Blind playthrough.
I have many questions at this point...why do we keep trading one type of gun for another? Why are we introduced to new mechanics and never seen them again after one or two uses? Why does chapter 2 take up over half of the gameplay? Why am I still playing this game at all?
Portal: Forbidden Testing Tracks ("PFT") invites you to delve into an exciting community-created modification for Portal 2, brought to life by a dedicated solo developer and fellow Portal 2 enthusiast. Step into the shoes of Rachel, an intrepid test subject, as she embarks on a thrilling journey guided by the endearing personality core named "SAIC," through the enigmatic Forbidden Testing Track, Codename: "Quebeck Seven."

[@ldidok]

I liked the part in 18:45 where you died because you were slow, and the part at 37:41 when the video ended