Learn Spanish (Latin America): Ellos estaban arreglando el techo a las dos. - They were fixing the roof at two o'clock.

Both estaban arreglando (past continuous) and arreglaban (imperfect) can translate to "were fixing." However, using estaban plus the gerund strongly emphasizes that the action was actively in progress right at that exact moment (a las dos).

Why is estar in the imperfect tense (estaban) and not the preterite (estuvieron)?

When forming the past continuous, we use the imperfect tense of estar (like estaban) because it describes an ongoing background action. Using the preterite (estuvieron) is much less common and would mean the action lasted for a specific, completed period of time, rather than just describing what was happening as a snapshot at two o'clock.

How is the word arreglando formed?

It is the gerund (the "-ing" form) of the verb arreglar (to fix). To make the gerund for "-ar" verbs, you simply drop the -ar ending and add -ando.

Why does it say a las dos for "at two o'clock"?