"We are going to the museum now."
Translation:Idziemy teraz do muzeum.
Is the "teraz" even needed given that we have been told over and over that "Idziemy" implies we are going right at that specific time? It would seem that putting teraz in the sentence at all is an emphasis on now. Am I correct?
The rule of thumb is that "do" + Genitive is rather used with buildings that you can enter and "na" + Accusative is used with open spaces. But that's very far from being a strict rule. For example you also have "na pocztę" for "to the post office" although it's a building. Or "do lasu" and "do parku" for "to the forest" or "to the park". Hmm, the more I think about it the worse this 'rule' seems :D
As it's 'we are going' (right now or 'we are planning to go'), Present Continuous, it's either "idziemy" (on foot) or "jedziemy" (by a vehicle).
"idziemy" can be also used if you're going to take a vehicle but do not consider it relevant at all. And as not many people have a museum close enough to their house to walk, it's a very common thing to use it that way.
"jeździmy" (Ź with an accent, not Ż with a dot) would be used for "We go to the museum every weekend".
Actually, this has nothing to do with the perfective/imperfective distinction. There are twelve verb pairs which show such a difference. In this case the two categories are called determinate/indeterminate.
However, if you combine those categories, the result might be a bit unexpected: