A superset is a set of an exercise, performed immediately after a set of another exercise, with little or no rest in-between.
Therefore, to perform the A-list exercises, you would first perform five consecutive reps of bench press followed immediately or with little rest of 5 consecutive reps of dumbbell flyes, followed by resting for 120 seconds. You would repeat this process five times (five sets of each exercise or five ‘supersets’) and then move on to the b-list exercises.
As you describe it, [quote]should be 5 reps A1 and immediately change to 5 reps of the A2 flat dumbbell flies exercise to complete de 5x5 rutine. [/quote]
Also, your English could use some work. Keep reading and posting. Just… make sure you read more than you post.