После моего вопроса она сделала глубокий вздох и ничего не сказала.

Because после requires the genitive.

So:

• после = after
• мой вопрос = my question
• after my question → после моего вопроса

This is a fixed grammar pattern in Russian:
после + genitive

More examples:

• после урока = after the lesson
• после работы = after work
• после встречи = after the meeting

Because мой has to agree with the noun in case, gender, and number.

The noun here is вопроса, which is:

• masculine
• singular
• genitive

So мой changes to моего.

A quick comparison:

• мой вопрос = my question (nominative)
• после моего вопроса = after my question (genitive)

Because вопрос is a masculine noun, and in the genitive singular many masculine nouns take -а.

So:

• вопрос = question
• вопроса = of the question / after the question

This is a very common pattern:

• стол → стола
• дом → дома
• урок → урока

Сделала is the perfective form, which presents the action as a completed single event.

Here the sentence describes a sequence of finished actions:

1. she took a deep breath
2. she said nothing

So perfective fits naturally:

• сделала глубокий вздох = she took a deep breath
• не сказала = she did not say anything

If you used делала, it would sound more like an ongoing, repeated, or process-focused action, which does not fit well here.

Yes, both are possible.

• сделала глубокий вздох = literally made/took a deep breath
• глубоко вздохнула = sighed/breathed in deeply

The version in your sentence is a noun-based expression, similar to English take a breath.

Both are natural, but they feel slightly different:

• сделала глубокий вздох sounds a bit more descriptive or literary
• глубоко вздохнула is often a bit simpler and more direct

Because сделала takes a direct object, and that object is in the accusative case:

• вздох → accusative singular: вздох

Since вздох is a masculine inanimate noun, its accusative form looks the same as the nominative.

The adjective must agree with it:

• nominative: глубокий вздох
• accusative (inanimate masculine): глубокий вздох

So the phrase stays глубокий вздох.

Because Russian normally uses double negation.

In English, we usually say:

• She didn’t say anything

In Russian, the natural pattern is:

• Она ничего не сказала

Literally, it looks like she nothing not said, but this is standard Russian grammar.

Other examples:

• Я никого не видел = I didn’t see anyone
• Мы никогда не спорим = We never argue

So with words like ничего, никого, никогда, нигде, Russian normally also uses не with the verb.

Because сказать and говорить are different in aspect and usage.

• сказать = to say, to tell; usually a single completed utterance
• говорить = to speak, to talk, to be speaking; more process-oriented or repeated

Here the meaning is that she did not say anything at all in that moment, so не сказала is the normal choice.

Compare:

• Она ничего не сказала. = She said nothing.
• Она ничего не говорила. = She wasn’t saying anything / She did not speak.

Both are possible in some contexts, but не сказала fits this one best.

Yes. Even though the Russian literally says after my question, English often prefers a verbal translation:

• После моего вопроса = after my question
• more natural English in context: After I asked my question or After my question

Russian often uses a noun phrase where English might use a clause.

Because и here connects two predicates with the same subject:

• она сделала глубокий вздох
• (она) ничего не сказала

Since both actions belong to the same subject она, no comma is needed.

So the structure is basically:

• She took a deep breath and said nothing.

Yes. Russian word order is flexible, and changing it can shift emphasis.

Original:

• После моего вопроса она сделала глубокий вздох и ничего не сказала.

This is neutral and natural.

Possible variants:

• Она после моего вопроса сделала глубокий вздох и ничего не сказала.
• Ничего не сказала она после моего вопроса, только сделала глубокий вздох.
  This sounds more marked or dramatic.

So the original word order is probably the most straightforward choice for a learner.

Because the subject is она = she.

In the past tense, Russian verbs agree with the subject in gender and number:

• он сказал = he said
• она сказала = she said
• оно сказало = it said
• они сказали = they said

The same happens with сделала:

• он сделал
• она сделала

They are close, but not identical.

• ничего не сказала = said nothing
• промолчала = kept silent / remained silent

Промолчала is more compact and can sound a bit more literary or expressive.
Ничего не сказала is very direct and transparent.

So this sentence could also be phrased as:

• После моего вопроса она глубоко вздохнула и промолчала.

But the original version is perfectly natural and slightly more explicit.