Ты напрасно волновалась: преподавательница уже видела твой отчёт и осталась довольна.

In the Russian past tense, singular verbs show gender. So волновалась tells you that the speaker is talking to one female person.

• to a woman: Ты волновалась
• to a man: Ты волновался

The same thing happens later in the sentence:

• видела is feminine because преподавательница is female
• осталась is also feminine for the same reason

It marks the verb as reflexive. The full infinitive is волноваться.

Compare:

• волновать = to worry / upset someone
• волноваться = to worry, be nervous, be anxious

So волновалась means was worrying / was anxious / was nervous.

The forms -ся and -сь are just two versions of the same ending. After a vowel, Russian often uses -сь, so you get волновалась, not волновалася.

Yes. Напрасно means in vain, for nothing, needlessly. It is very close to зря.

So:

• Ты напрасно волновалась = You worried for nothing
• Ты зря волновалась = almost the same thing

A rough difference is that напрасно can sound a little more neutral or slightly more bookish, while зря is very common in everyday speech.

The second part explains or justifies the first part.

The logic is:

You worried for nothing: the teacher had already seen your report and was pleased.

In Russian, a colon is often used when the second clause gives the reason, explanation, or evidence for what was just said.

Преподавательница is the explicitly feminine form and means female teacher / female instructor / female lecturer.

It matches the feminine verb forms:

• видела
• осталась

You may also see преподаватель used more generally, but преподавательница clearly tells you the teacher is a woman.

Because видела from видеть often expresses the fact that someone had seen something already.

Here the important idea is not the exact moment when the teacher first noticed the report, but simply that she had already seen it. So уже видела sounds very natural.

If you used увидела, the focus would shift more toward a single completed moment of noticing or seeing.

Russian does not have a separate tense that works exactly like the English present perfect.

So a simple past form like видела can correspond to English:

• saw
• has seen

That is why уже видела can naturally mean has already seen.

It is in the accusative, but for a masculine inanimate noun, the accusative singular looks the same as the nominative singular.

So:

• nominative: твой отчёт
• accusative: твой отчёт

That is why you do not see any change here.

Because the stressed vowel in this word is ё. The word is pronounced отчёт, with the stress on that syllable.

In many printed texts, Russians often write е instead of ё, so you may also see отчет. But the pronunciation is still отчёт.

Literally:

• осталась = remained / stayed
• довольна = satisfied / pleased

Together, осталась довольна means:

• was pleased
• ended up satisfied
• was happy with it

Довольна is the short-form adjective, feminine singular. Russian often uses short-form adjectives in predicate position, especially with meanings like pleased, ready, sure, happy, satisfied. In this sentence, осталась довольна is the normal, idiomatic phrasing.

Because the subject is still преподавательница, so repeating a pronoun is unnecessary.

Russian often leaves out a repeated subject when it is already clear:

преподавательница уже видела твой отчёт и осталась довольна

The meaning is still:

the teacher had already seen your report and was pleased

but Russian does not need to add она again.