Complex sentence: From the quarter final round it is a purely knockout competition where ties take place over 1-leg only, if a tie is not decided in the 90 minutes and extra-time then penalty kicks are taken to decide the game.
Split into simpler sentences: From the quarter final round it is a purely knockout competition where ties take place over 1-leg only. If a tie is not decided in 90 minutes, penalty kicks are taken to decide the game.