Breakdown of Он долго шёл вдоль высокого забора.
он
he / it (for a masculine noun) / it (for a neuter noun)
высокий
tall / high (of a level or amount)
идти
to go (on foot) / to proceed, go (of a process)
долго
for a long time
Questions & Answers about Он долго шёл вдоль высокого забора.
Why are высокого and забора in the Genitive case?
The preposition вдоль (along) always requires the Genitive case. As a result, the masculine noun забор (fence) takes the -а ending, and its describing adjective высокий (high) takes the masculine Genitive ending -ого.
How is the adjective высокого pronounced here?
As a quick reminder, the -ого ending for masculine and neuter Genitive adjectives is pronounced with a "v" sound instead of a "g". It sounds like высоково (vysokovo).
Why does the sentence use шёл instead of the other past-tense walking verb, ходил?
Шёл is the unidirectional verb of motion. It is used here because the sentence focuses on a single, continuous trip moving forward in one direction (progressing down the length of the fence). Ходил would imply walking back and forth or making multiple trips.
Where is the word for "for" in the phrase "for a long time"?
Russian doesn't need a preposition here. The single adverb долго translates directly to the entire phrase "for a long time" when describing how long an action took.