После пары я зашёл в буфет и купил йогурт.

После means after, and it requires the genitive case.

So:

• пара = a class period / a double lesson
• после пары = after the class / after the lesson

This is why you see пары, not пара.

A few similar examples:

• после урока = after the lesson
• после работы = after work
• после фильма = after the film

So the pattern is:

• после + genitive

Yes, пара often means pair, but in student/university speech it also commonly means a class period, especially a longer one made up of two academic hours.

So in this sentence, после пары does not mean after a pair. It means something like:

• after class
• after the lesson
• after a university session

This is a very common educational-context meaning of пара in Russian.

Зайти / заходить often means to drop in, to stop by, or to go in for a short time.

So:

• пошёл в буфет = went to the cafeteria/buffet
• зашёл в буфет = dropped into the cafeteria / stopped by the cafeteria

In this sentence, зашёл suggests a quick visit on the way somewhere or as a brief action after class. It sounds very natural here.

So the nuance is:

• пойти = go
• зайти = go in / stop by / drop in

Because Russian uses different cases depending on whether you mean:

• movement to a place
• location in a place

Here, the speaker is going into the buffet/cafeteria, so Russian uses:

• в + accusative → в буфет

Compare:

• Я зашёл в буфет. = I went into / dropped by the buffet.
• Я был в буфете. = I was in the buffet.

So:

• в буфет = destination
• в буфете = location

Not exactly in the English restaurant sense.

In Russian, буфет can mean a small food counter, snack bar, or cafeteria-style place, especially in a school, university, theater, or workplace.

So here it probably means something like:

• cafeteria
• snack bar
• canteen counter

It does not necessarily mean an all-you-can-eat buffet.

Both verbs are in the past tense:

• зашёл = went in / stopped by
• купил = bought

In Russian past tense, the form also shows gender in the singular.

Here:

• зашёл = masculine
• купил = masculine

So the speaker is male.

If the speaker were female, it would be:

• После пары я зашла в буфет и купила йогурт.

This is a very important feature of Russian past tense.

Because the sentence describes two completed actions:

1. he stopped by the buffet
2. he bought a yogurt

Perfective verbs are commonly used for single, completed events in a sequence.

Here:

• зайти → зашёл = completed act of going in
• купить → купил = completed act of buying

If you used imperfective forms, the meaning would change. It might sound more like process, habit, or background action.

Compare:

• Я зашёл в буфет и купил йогурт. = I stopped by the buffet and bought a yogurt.
• Я заходил в буфет и покупал йогурт. = I used to go to the buffet and buy yogurt / I went there and was engaged in that kind of action.

So perfective is the natural choice for a simple finished story.

Because йогурт is:

• masculine
• inanimate
• singular

For many masculine inanimate nouns, the accusative singular is the same as the nominative singular.

So:

• nominative: йогурт
• accusative: йогурт

That is why the sentence says:

• купил йогурт

Compare with an animate masculine noun:

• Я вижу студента. = I see the student.

There, the accusative changes because студент is animate.

Good question. Пары can indeed look ambiguous:

• nominative plural of пара
• genitive singular of пара

But after после, it must be genitive, so here it is:

• genitive singular: после пары

So even though the form looks like a plural, the grammar tells you it is singular here.

И simply means and, linking the two completed actions.

The order is important because it reflects the sequence:

1. зашёл в буфет
2. купил йогурт

So the sentence tells a small chain of events: after class, he dropped by the cafeteria and then bought yogurt.

Russian often uses this simple past verb + и + past verb pattern to narrate actions in order.

Yes. Russian word order is flexible, although each version can sound slightly different in emphasis.

The sentence:

• После пары я зашёл в буфет и купил йогурт.

is very natural and neutral.

Other possible orders:

• Я после пары зашёл в буфет и купил йогурт.
• В буфет я зашёл после пары и купил йогурт.

These alternatives may shift emphasis slightly:

• После пары first emphasizes when
• я earlier can emphasize who
• в буфет first can emphasize where

But the original version is a very normal default way to say it.

Because Russian has no articles like a or the.

So купил йогурт could mean:

• bought a yogurt
• bought the yogurt

Which one is meant depends on context.

In many beginner sentences like this, English usually translates it as a yogurt, because that sounds most natural without additional context.

The correct spelling is зашёл, with ё.

This matters because ё shows both:

• the correct pronunciation
• the stress

So it is pronounced roughly like za-SHYOL.

In informal writing, Russians sometimes replace ё with е, so you may also see зашел, but the intended word is still зашёл.

For learners, it is helpful to remember the proper form with ё, especially because it makes pronunciation clearer.