Learn Hardcore Russian: Я не волнуюсь, когда говорю по-русски.

по-русски is not a prepositional phrase but an adverb meaning “in Russian” or “in a Russian manner.” It’s formed with the prefix по- + the neuter short form of the adjective русский + suffix -и. You see the same pattern in по-английски, по-испански, etc.

Why is волнуюсь reflexive instead of a simple verb like волную?

The base verb волновать is transitive (“to cause someone to worry”), so it needs a direct object. To say “I worry” you use the reflexive волноваться, which literally means “to make oneself worried.” The -ся ending turns it into an intransitive form meaning “to experience worry.”

What aspect and tense is говорю, and why is that appropriate here?

говорю is the present tense, imperfective aspect of говорить. Imperfective aspect expresses an ongoing or repeated action. Here it conveys “when I am speaking (on any occasion) in Russian,” not a single completed instance.

Why do we use когда plus a clause instead of an infinitive construction like “to speak”?

Using когда + clause highlights the time frame: “whenever/as I speak.” An infinitive construction (не волнуюсь говорить) would be understood but sounds less natural and shifts focus to the action of speaking rather than the timing.

Is the comma before когда mandatory, and can we change the word order?

Yes, the comma separates the main clause Я не волнуюсь from the subordinate clause когда говорю по-русски. You can invert the clauses:
– Когда говорю по-русски, я не волнуюсь.
The comma still appears before the main clause.

Why is не placed before волнуюсь, and could we say волнуюсь не?

In Russian, не is normally placed immediately before the verb to negate it: не + волнуюсь. Placing не after (волнуюсь не) is ungrammatical unless you add another element for contrast (волнуюсь не тогда, когда…).

Can we use беспокоюсь instead of волнуюсь? What’s the difference?

Both беспокоиться and волноваться mean “to worry,” but there’s a nuance:

беспокоиться often implies concern about something specific (“I worry about the test”).
волноваться can be more general or emotional (“I get nervous”).
In this sentence не волнуюсь emphasizes “I don’t get nervous.”

Could we say Я не волнуюсь говорить по-русски, and would that change the meaning?

You could say Я не волнуюсь говорить по-русски, but it’s less idiomatic. It uses an infinitive after волнуюсь, shifting focus to the act of speaking rather than the timing. Native speakers almost always prefer когда говорю for “when I speak.”