Breakdown of O que estavas a fazer quando o crime aconteceu?
o que
what
estar
to be (temporary / location)
quando
when
fazer
to do
Questions & Answers about O que estavas a fazer quando o crime aconteceu?
How does estavas a fazer translate to "were you doing"?
This is the Portuguese past continuous tense. In Portugal, we build it using the imperfect past tense of estar (here, estavas for the informal "you"), the preposition a, and the infinitive of the main action verb (fazer).
Why do we use two different past tenses in this sentence (estavas vs. aconteceu)?
We use the past continuous (estavas a fazer) to describe an ongoing background action ("were doing"). We use the simple past for aconteceu because the crime happening was a sudden, completed event that interrupted what you were doing.
Why does the sentence start with O que instead of just Que for "What"?
Where is the word for "you" in this sentence?
It is built right into the verb! The form estavas is specifically the tu (informal "you") conjugation of estar in the imperfect tense. Because the verb ending makes the subject obvious, the word tu is left out.