Black wins with EXACTLY five — no more. Six or more in a row is an overline: for white a perfectly good win, for black a forbidden move, judged the instant the stone lands. Here black already holds 3+2 on one row with a single gap, and the gap point is the trap: every instinct says fill it, but filling it lays six black stones in a row and loses on the spot. White players spend their careers feeding black exactly this gift. Find it.
Finish this step to move on.