Breakdown of We waren aan het filmen totdat de regisseur kwam.
zijn
to be
komen
to come
aan
on / at (attached to, edge)
we
we (unstressed form of wij)
Questions & Answers about We waren aan het filmen totdat de regisseur kwam.
Why do we use waren aan het filmen instead of just filmden?
waren aan het filmen translates to "were filming" and emphasizes that the action was actively in progress. It sets a continuous background scene that gets interrupted by the next event (the director arriving).
How exactly is this past continuous phrase built?
You use the simple past tense of the verb zijn (to be) - which is waren because the subject is we - followed by the fixed phrase aan het, and finally the full infinitive of the action verb (filmen).
Why does the verb kwam get pushed to the very end of the sentence?
The word totdat (until) introduces a dependent (subordinate) clause. In Dutch, a dependent clause always sends its conjugated verb to the end of the clause. Here, kwam (came) is pushed to the end after the subject de regisseur.
Could I just use tot instead of totdat?
When you are connecting a full clause that has its own subject and verb (like de regisseur kwam), it is much better and more common to use totdat. You usually use tot when placing it right before a noun or a specific time, like in the phrase tot morgen (until tomorrow).