Learn Hardcore Russian: Я открыл папку и прочитал документ. - I opened the folder and read the document.

In Russian, the direct object of a transitive verb takes the accusative case. Here папку is what you “opened,” so it’s in accusative. You recognize accusative feminine singular by the ending –у (from nominative папка → accusative папку).

Why do открыл and прочитал end in -л, and why don’t they show person (1st, 2nd, 3rd)?

Russian past tense is formed by adding gender/number endings to the verb’s perfective or imperfective stem. Both открыл and прочитал are masculine singular past forms (–л), so they agree in gender with a male speaker. Past tense in Russian does not mark person; it marks only gender and number.

When should I use the perfective verbs открыть and прочитать instead of their imperfective counterparts открывать and читать?

Use the perfective aspect (infinitives открыть, прочитать) when you want to express completed actions. The imperfective (infinitives открывать, читать) describes ongoing or repeated actions. Here you opened the folder once and finished reading the document, so perfective is appropriate.

Could this sentence be written with imperfective verbs, like Я открывал папку и читал документ?

Grammatically yes, but the meaning shifts. Я открывал папку и читал документ suggests you were in the process of opening the folder and reading the document (perhaps repeatedly or simultaneously), not that you completed each action.

Can I drop the pronoun я and just say Открыл папку и прочитал документ?

Yes. In Russian the subject pronoun can often be omitted if the verb form (here past masculine singular) makes it clear who is doing the action. Omitting я gives a more concise, informal tone.

Why is there no preposition in прочитал документ? Which case does документ take?

When you read something (verb читать/прочитать), that thing is a direct object in the accusative case. Документ (nominative) becomes документ (accusative for masculine inanimate nouns stays the same as nominative). No preposition is needed.

Could I swap the order and say Я прочитал документ и открыл папку?

You can grammatically, but it changes the sequence of events. Your original means “I opened the folder first, then read the document.” Swapping implies you read the document before opening the folder, which is logically odd if that document was inside the folder.

Does the sentence explicitly state that the document was inside the folder?

Not in strict grammatical terms—Russian doesn’t require a preposition like “из” here—but by context it’s implied that you opened the folder to get at the document. If you needed to stress “from the folder,” you could say Я открыл папку и вынул/прочитал документ or …прочитал документ из папки.