haha ga isogashii toki, watashi wa bangohan o tsukutte agemasu.

This is a very common question.

• 母が忙しい = my mother is busy
• 私は = as for me

Here, が marks the subject inside the when clause: 母が忙しいとき means when my mother is busy.

Then は marks the main topic of the sentence: 私は晩ご飯を作ってあげます means I make dinner for her.

So the sentence is structured like this:

• 母が忙しいとき = when my mother is busy
• 私は晩ご飯を作ってあげます = I make dinner for her

A rough natural breakdown is:

• When my mother is busy, I make dinner for her.

Using 母は忙しいとき would sound different and less natural here, because 母 is not the main topic of the whole sentence.

とき means time or when, and it attaches to a clause.

So:

• 忙しいとき = when someone is busy
• 母が忙しいとき = when my mother is busy

The clause before とき describes the situation at that time.

You can think of it as:

• [mother is busy] + time/when

This is a very common pattern in Japanese:

• 暇なとき = when someone is free
• 行くとき = when going
• 食べたとき = when someone ate / when someone had eaten

Because 忙しい is an い-adjective, and before とき you use the adjective in its normal plain form.

So:

• 忙しいとき = when busy

You do not change it to 忙しく here.

Compare:

• 高い山 = a high mountain
• 忙しいとき = when busy

In both cases, the adjective directly modifies the noun that follows it:

• 山
• とき

Since とき is a noun, 忙しい directly describes it.

作ります simply means make or cook.

作ってあげます adds the idea of doing it for someone as a favor / for their benefit.

So:

• 晩ご飯を作ります = I make dinner
• 晩ご飯を作ってあげます = I make dinner for someone

In this sentence, that someone is understood to be the mother.

So あげます adds a benefactive meaning: the action is done for another person.

This is a very important Japanese pattern:

• Vてあげる = do something for someone
• Vてもらう = receive the favor of someone doing something
• Vてくれる = someone does something for me/us

In this sentence, the receiver is understood from context: it is the mother.

So even though Japanese does not explicitly say 母に, the meaning is:

• When my mother is busy, I make dinner for her.

Japanese often leaves out information that is obvious from context.

If you wanted to say it more explicitly, you could say:

• 母が忙しいとき、私は母に晩ご飯を作ってあげます。

But this sounds a little repetitive, so the shorter version is more natural.

Good question. Vてあげます can sometimes sound like the speaker is presenting their action as a favor, so in some situations it may sound a bit self-centered or condescending.

In this sentence, though, it is generally natural, because:

• the speaker is talking about helping their mother
• the action is clearly beneficial to her
• the sentence is just describing what they do

So 作ってあげます is fine here.

Still, depending on tone and context, some speakers might simply say:

• 母が忙しいとき、私は晩ご飯を作ります。

That sounds more neutral.

So the difference is:

• 作ります = neutral statement
• 作ってあげます = emphasizes that it is done for her benefit

Yes, 私 could be omitted.

Japanese often leaves out subjects and topics when they are clear.

So these can both work:

• 母が忙しいとき、私は晩ご飯を作ってあげます。
• 母が忙しいとき、晩ご飯を作ってあげます。

The version with 私は is a little clearer and gives contrast or emphasis to I.

It can feel like:

• When my mother is busy, I am the one who makes dinner for her.

So 私は is not required, but it is perfectly natural.

を marks the direct object of the verb.

Here, the thing being made is 晩ご飯:

• 晩ご飯を作る = to make dinner

So:

• 晩ご飯 = dinner
• を = object marker
• 作ってあげます = make for someone

Very literally:

• Dinner + object marker + make for someone

Because this uses the て-form pattern:

• 作る → 作って
• 作ってあげます = do the action of making, then add あげます

This is how Japanese connects one verb to a helping or auxiliary verb.

The pattern is:

• Vて + あげる

Examples:

• 教えてあげる = teach someone / do the favor of teaching
• 買ってあげる = buy something for someone
• 作ってあげる = make something for someone

So 作って is not a separate meaning by itself here; it is the form needed before あげます.

Yes, 晩ご飯 means dinner / evening meal.

It is very similar to 夕飯. In everyday Japanese, both are common.

Very roughly:

• 晩ご飯 = dinner
• 夕飯 = dinner / supper

The nuance is small, and in most contexts either one would be understood.

Also, ご飯 originally means cooked rice, but very often it means meal in compounds like this.

So here 晩ご飯 means the whole evening meal, not just rice.

When talking about your own mother to other people, Japanese often uses 母.

• 母 = my mother
• お母さん = mother / mom, often when addressing her directly or referring to someone else’s mother in a polite/friendly way

So in a sentence describing your own family situation, 母 is very natural.

A simple rule of thumb:

• talking to your mother: お母さん
• talking about your own mother to others: 母

It is in the non-past form, which can cover several English ideas depending on context.

• 忙しい = is busy / will be busy
• 作ってあげます = make for her / will make for her

In this sentence, the most natural reading is often habitual:

• When my mother is busy, I make dinner for her.

But it could also describe a future situation, depending on context:

• When my mother is busy, I’ll make dinner for her.

Japanese non-past forms are flexible like that.

No, it is not strictly necessary, but it is very common and helpful.

So both are possible:

• 母が忙しいとき、私は晩ご飯を作ってあげます。
• 母が忙しいとき私は晩ご飯を作ってあげます。

The comma makes the sentence easier to read by clearly separating the when clause from the main clause.

In writing, Japanese commas are often used for clarity rather than fixed grammar rules.

No, not really.

In 作ってあげます, the あげます does not mean physically give the dinner. It means do the action for someone’s benefit.

So the meaning is:

• I cook dinner for her
• not I cook dinner and hand it over to her

This is one of the most important things to understand about Vてあげる: it is a grammar pattern meaning do something for someone, not two separate actions.

Yes, you can.

Both are possible:

• 母が忙しいとき、私は晩ご飯を作ってあげます。
• 母が忙しいときに、私は晩ご飯を作ってあげます。

The に can mark the time more explicitly, but with とき it is often omitted, especially in natural everyday speech.

In many cases:

• とき = perfectly natural
• ときに = also correct, sometimes a bit more marked or formal depending on context

So the version without に is very normal here.