Breakdown of Die Maschine wurde vom Mechaniker am schnellsten repariert.
schnell
fast, quickly
vom
from the (von + dem) / of the (belonging to) / by the (agent in a passive clause)
reparieren
to repair
am
the most (superlative marker)
Questions & Answers about Die Maschine wurde vom Mechaniker am schnellsten repariert.
Why do we use vom here to say "by", rather than durch?
In passive sentences, we use von when the agent (the one doing the action) is a person, animal, or active institution that intentionally performs the action. Because the mechanic is a person consciously doing the repairing, we use von. We would use durch for a tool, an abstract cause, or a means (like durch einen Sturm - by a storm).
Where exactly does the word vom come from in this sentence?
vom is a mandatory contraction of the preposition von and the definite article dem. The preposition von always requires the dative case. Since Mechaniker is a masculine noun, its dative article is dem, and von dem naturally merges into vom.
Why does the sentence use am schnellsten instead of just das schnellste for "the fastest"?
Here, "fastest" describes how the machine was repaired, which makes it an adverb modifying the verb. In German, when a superlative describes an action rather than a specific noun, you must use the structure am + [adjective/adverb] + -sten. Therefore, schnell becomes am schnellsten.
How can I tell this is the simple past (Präteritum) passive and not the present passive?