Drain pipe P trap leaking under sink
Your P trap is put together backward! The bent piece (called the "outlet") is supposed to come off of the SHORT side of the trap. If you look, the side where your outlet is connected now in that picture has a long wider section at the top. THAT is where your tailpiece (the straight part coming down from the sink) is supposed to go, it's wider so that the tailpiece fits down in there before you then clamp around it with the tapered washer.