После занятия я поняла, что инструкцию по безопасности лучше читать заранее, а не во время тревоги.

Because после requires the genitive case.

The noun занятие is neuter, and its genitive singular form is занятия.

• nominative: занятие
• genitive: занятия

So:

• после занятия = after the class / after the session

This is a very common pattern in Russian:

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

Because the past tense in Russian agrees with the speaker’s gender in the singular.

• я понял = I realized / understood (said by a man)
• я поняла = I realized / understood (said by a woman)

So this sentence is spoken by a female speaker.

Here it most naturally means realized.

Although понять / поняла often means to understand, in sentences like this it often has the sense of coming to a conclusion or recognizing something:

• Я поняла, что... = I realized that...

That sounds more natural in English here than I understood that...

Что introduces a subordinate clause, just like that in English.

• Я поняла, что... = I realized that...

Everything after что is the content of what the speaker realized.

This is one of the most common uses of что in Russian.

Because инструкцию is the accusative singular form. It is the direct object of читать.

The basic form is:

• инструкция = instruction / manual / guidelines

But after a verb like читать (to read), you need the direct object:

• читать инструкцию = to read the instructions / manual

So:

• nominative: инструкция
• accusative: инструкцию

In инструкция по безопасности, the preposition по means something like on, regarding, or for in English.

So:

• инструкция по безопасности = safety instructions / instructions on safety

After по in this meaning, Russian usually uses the dative case.

The noun is:

• безопасность = safety

Its dative form is:

• безопасности

So the phrase is:

• инструкция по безопасности

This is a fixed and very common type of expression:

• книга по истории = a book on history
• экзамен по математике = an exam in math
• советы по питанию = advice on nutrition

This is mainly about aspect.

• читать = imperfective, focuses on the process or general action of reading
• прочитать = perfective, focuses on reading something through to completion

In a sentence giving general advice, Russian often prefers the imperfective infinitive after лучше:

• лучше читать заранее = it is better to read in advance

This sounds like general wisdom or advice: the sensible thing is to do the reading beforehand.

If you said лучше прочитать заранее, that is also possible, but it would sound a bit more focused on finishing the reading before the emergency.

So:

• лучше читать = better to be reading / better to read, as general advice
• лучше прочитать = better to read it completely

Yes. In Russian, лучше + infinitive is a very common structure meaning it’s better to...

So:

• лучше читать заранее = it’s better to read in advance

You do not need надо here.

Compare:

• Надо читать заранее = one should read in advance / it is necessary to read in advance
• Лучше читать заранее = it is better to read in advance

Лучше expresses recommendation or wiser choice, not strict necessity.

Заранее means in advance, beforehand, or ahead of time.

So:

• читать заранее = to read beforehand

It is an adverb, so it modifies the verb читать.

Examples:

• Я приготовил всё заранее. = I prepared everything in advance.
• Лучше спросить заранее. = It’s better to ask beforehand.

Because а не creates a contrast: this, not that.

Here the speaker is contrasting two moments:

• заранее = beforehand
• во время тревоги = during the alarm/emergency

So:

• лучше читать заранее, а не во время тревоги
  = it’s better to read beforehand, not during an alarm

Using а не makes the correction or contrast very clear. It is similar to English rather than or and not / not ... but rather ...

This uses the fixed expression во время + genitive, which means during.

The noun is:

• тревога = alarm, alert, emergency alarm, air-raid alarm, anxiety (depending on context)

Its genitive singular form is:

• тревоги

So:

• во время тревоги = during the alarm / during the emergency

This is another very common pattern:

• во время урока = during the lesson
• во время встречи = during the meeting
• во время войны = during the war

In this sentence, тревога most likely means an alarm or emergency alert, not the emotional state of anxiety.

Russian тревога can mean:

• anxiety
• alarm / alert
• emergency signal

Because the sentence talks about reading safety instructions, во время тревоги clearly means something like during an alarm or during an emergency alert.

Yes. Russian word order is more flexible than English, although the original version sounds natural and balanced.

Original:

• После занятия я поняла, что инструкцию по безопасности лучше читать заранее, а не во время тревоги.

Possible variations:

• Я поняла после занятия, что...
• Инструкцию по безопасности лучше читать заранее, а не во время тревоги, я поняла после занятия.

But the original order is good because it presents the sentence in a clear progression:

1. После занятия = time/background
2. я поняла = main action
3. что... = what was realized
4. contrast: заранее, а не во время тревоги

Not always. Занятие can mean several related things:

• class
• lesson
• session
• activity
• training session

In this sentence, после занятия most likely means after the class or after the session.

The exact translation depends on context. For example:

• at school: after the lesson/class
• in training: after the session
• in a workshop: after the workshop session

So it is a flexible word, and English may translate it differently depending on the situation.