Learn Hardcore Russian: После урока он спокойно разговаривает со студентами в коридоре. - After the lesson he calmly talks with the students in the corridor.

разговаривать – to have a conversation, to chat, to talk with someone
- Emphasizes a two-way interaction.
- Common with с кем?: разговаривать со студентами (talk with the students).
говорить – to speak, to say (more general)
- Can be one-way: говорить правду (to tell the truth), говорить по-русски (to speak Russian).
- Can also be used with с кем?: говорить со студентами (to talk with the students).

In this sentence разговаривает со студентами highlights the idea of a friendly, two-sided conversation.

Why is it со студентами, not с студентами?

The basic preposition is с (with), but Russian uses the longer form со in front of some words to make pronunciation easier, especially:

Before с, з, ш, ж or sometimes ст-, ск- etc.

Студентами starts with ст-, so со студентами is smoother than с студентами, which is hard to pronounce.

Other examples:

со мной (with me)
со статьёй (with the article)
со шкафом (with the cupboard)

What case is студентами, and what does that case mean here?

Студентами is:

Plural of студент (student)
Instrumental case plural

The instrumental case is used after с / со to mean with someone / something.

So:

Nominative plural: студенты (students)
Instrumental plural: студентами (with the students)

со студентами = with the students.

Why do we say в коридоре and not в коридор?

The preposition в can take:

Accusative case – direction / motion into a place
- в коридор – into the corridor
Prepositional case – location in / inside a place
- в коридоре – in the corridor

In the sentence, he is already located in the corridor while talking, so Russian uses в коридоре (prepositional, location), not в коридор (motion).

What case is коридоре, and how is it formed?

Коридоре is:

From коридор (corridor, hallway)
Prepositional case singular

For many masculine nouns ending in a consonant:

Nominative: коридор
Prepositional (with в, на for location): в коридоре

Pattern: add -е for the prepositional singular:

город → в городе (in the city)
театр → в театре (in the theater)
коридор → в коридоре (in the corridor)

What exactly does спокойно mean here? Is it calmly, quietly, or something else?

Спокойно is an adverb from спокойный (calm). It usually means:

calmly
without tension
in a relaxed, unhurried way
also often “without causing a disturbance / fuss”

In this context, он спокойно разговаривает implies he is talking in a calm, relaxed manner, not angrily, nervously, or loudly.
If you wanted to emphasize quietly (low volume), you’d more typically say он тихо разговаривает.

Can I move спокойно to another position, like он разговаривает спокойно? Does it change the meaning?

Yes, Russian word order is flexible, and both are correct:

Он спокойно разговаривает со студентами…
Slightly emphasizes how he talks (the calmness is foregrounded).
Он разговаривает спокойно со студентами…
Slightly more neutral order; the focus feels more on the action разговаривает, with спокойно just describing it.

The basic meaning (he talks calmly with the students) stays the same; the difference is subtle and mostly about rhythm and slight emphasis.

Can I drop он and just say После урока спокойно разговаривает со студентами в коридоре?

Yes, grammatically you can omit the subject pronoun in Russian because the verb ending already shows the person and number:

разговаривает – clearly he/she/it (3rd person singular)

So the sentence without он is still correct Russian and often natural if the person is already clear from context.

However, in isolation (as a standalone sentence), Russians usually include он so the subject is explicit:
После урока он спокойно разговаривает со студентами в коридоре.

How is разговаривает pronounced, and where is the stress?

Разговаривает is pronounced with the stress on the -ва- syllable:

раз-го-ва-ри-ва-ет
IPA (approx.): /rəzɡɐˈvarʲɪvɐjɪt/

Other words in the sentence (with stressed syllable in caps):

ПО́сле
уро́КА
он
споко́Йно (actually: спокОйно – stress on -кой-)
разгова́ривает
СО студентами (студе́нтами – stress on -де́н-)
в коридо́ре

Knowing the stress pattern helps you recognize and produce the verb forms more easily.

Why is it разговаривает, not something like разговорит?

Разговаривать is an imperfective verb. Its present-tense forms are:

я разговариваю
ты разговариваешь
он/она разговаривает
мы разговариваем
вы разговариваете
они разговаривают

There is a different verb разговорить (perfective, very limited usage), but it does not mean to have a conversation in the regular sense; it’s more like “to get someone talking / to make someone talk.”

So for he talks / is talking (with someone), the correct form is он разговаривает.