It seems that in this section, at this point, only simple present is accepted. It has been the case with all the examples I have had so far. Reverse trend from earlier sections where strong preference of present continuous was dominant. Just confusing.
I don't know if this lesson has tips¬es or not, but if not, then it will probably be added in the future with an explanation to this.
The prefix adds a perfective aspect to the verb, which now implies that the action will be completed: we will end up on the second floor. If you wanted to express that we are hurrying down right now without implying any result, you could leave out the prefix: "Sietünk a második emeletre." Though "down" is missing from this sentence -- we could be on the ground floor and hurry to the second floor from there. To make it clear you can add "le" after the verb: "Sietünk le a második emeletre." or "Sietünk lefelé a második emeletre." (lit. "downwards")
This explanation makes sense. The next lesson has the following sentence: felrepülunk mi is. This is translated by: we are flying up too, and not by: we fly up too. I am not sure about the implication now, and if here the present continuous (are hurrying) should be rejected (it is currently) or accepted as an alternative answer.
What is the difference between: We hurry down to the second floor and We rush down to the second floor?