Hey Maria,
This is more of a Python question than a Rasa one.
random.shuffle()
(try it) shuffles a list, meaning it reorganizes its items. It does not randomly take one element.
Instead, you can shuffle the list and take the first element:
dispatcher.utter_message(text = random.shuffle(response)[0])
or use random.choice()
(try it) which is the method you’re looking for:
dispatcher.utter_message(text = random.choice(response))