haha ha itumo yori hayaku watasi wo okosita ga, watasi ha mata sukosi hirunesite simatta.

Yes. In Japanese, family words like 母 often mean my mother when the speaker is talking about their own family.

• 母 = my mother / one’s mother (humble, more neutral in narration)
• お母さん = mother / mom, often used when speaking to her or talking about someone else’s mother more politely

So in this sentence, 母は naturally means As for my mother, ...

より is used to show comparison, like than in English.

So:

• いつも = usually / always
• より = than

Together, いつもより means than usual or more literally than always/usual times.

In this sentence:

• いつもより早く = earlier than usual

This is a very common pattern:

• AよりB = B more than A / B than A
• 昨日より寒い = It’s colder than yesterday.
• 思ったより難しい = It’s more difficult than I thought.

Because 早い is an -い adjective, and here it is being used like an adverb to modify the verb 起こした.

• 早い = early
• 早く = early / quickly, in an adverbial form

So:

• 早い時間 = an early time
• 早く起こした = woke me up early

This is a common rule:

• -い adjective → replace い with く when modifying a verb

Examples:

• 速い → 速く走る = run fast
• 遅い → 遅く来る = come late

Because 私 is the object of 起こした.

• 起こす means to wake someone up
• The person being woken is marked with を

So:

• 母は私を起こした = Mother woke me up

If you said 私は起こした, that would mean I woke someone/something up (with the object left unstated), which is a different meaning.

So the structure is:

• 母は = as for my mother
• 私を = me
• 起こした = woke up

This is a very important distinction.

• 起きる = to wake up / get up oneself
• 起こす = to wake someone else up

So:

• 私は起きた = I woke up
• 母は私を起こした = My mother woke me up

In this sentence, the mother is doing the action to another person, so 起こした is the correct verb.

Here, が connects two clauses and has a contrastive meaning, so but is a good translation.

• 母はいつもより早く私を起こしたが、
• 私はまた少し昼寝してしまった。

= My mother woke me up earlier than usual, but I ended up taking another short nap.

A few notes:

• が is often a little softer or more literary than a strong but
• In everyday speech, many people might also use けど or けれども

So yes, but is the main idea here, but it can feel like a softer contrast: although / however / but then depending on context.

Yes, it could often be omitted in Japanese if the subject is obvious from context.

Possible version:

• 母はいつもより早く私を起こしたが、また少し昼寝してしまった。

That would still be understandable.

But 私は is included here to create a clearer contrast:

• 母は ... = as for my mother, she did this
• 私は ... = as for me, I did this

This makes the contrast between the two people more explicit and natural in a sentence with が.

また usually means again.

So here:

• また少し昼寝してしまった = ended up taking another short nap again

The idea is that even though the speaker was woken up, they went back to sleep again, at least briefly.

Depending on context, また can sometimes mean:

• again
• once more
• also

But in this sentence, again is the natural meaning.

Because 昼寝する is a very common noun + する verb expression.

• 昼寝 = nap
• 昼寝する = to take a nap

In the て-form, する becomes して:

• 昼寝して

You may also sometimes see 昼寝をする, which is not wrong. But 昼寝する is very common and natural.

So:

• 昼寝してしまった = ended up taking a nap

〜てしまう often adds one of these nuances:

1. completion: did something completely
2. regret / disappointment
3. accidental or unintended action

In this sentence, it most likely suggests something like:

• I ended up taking another nap
• I unfortunately went back to sleep
• I dozed off again without meaning to

So 昼寝した would just state the fact:

• I took a nap

But 昼寝してしまった suggests the speaker sees it as a bit regrettable, unintended, or contrary to what should have happened after being woken up.

That nuance is very common with 〜てしまう.

少し means a little or for a short while.

In this sentence, it naturally means the speaker napped a little bit / for a short time.

So:

• 少し昼寝してしまった = I ended up taking a short nap / I dozed off for a bit

It does not necessarily mean the nap was a formal, full daytime nap in the English sense. In context, it can simply mean the speaker drifted back to sleep for a little while after being woken up.

Good question. 二度寝 is indeed a very common word for going back to sleep after waking up once.

So in real-life Japanese, many people might say something like:

• また少し二度寝してしまった。

That would strongly emphasize I went back to sleep again after waking up.

However, 昼寝 in your sentence is still understandable if the intended meaning is that the speaker slept a little more, almost like a short nap. It may sound a bit less precise than 二度寝, depending on the context and time of day.

So:

• 昼寝 = nap
• 二度寝 = going back to sleep after waking up

If the situation is specifically someone woke me up, but I fell asleep again, 二度寝 is often the more idiomatic choice.

It breaks down like this:

• 母は = as for my mother
• いつもより = than usual
• 早く = early / earlier
• 私を = me
• 起こした = woke up
• が = but
• 私は = as for me
• また = again
• 少し = a little
• 昼寝してしまった = ended up taking a nap / ended up dozing off

So the basic structure is:

[Topic 1] [comparison] [adverb] [object] [verb], but [Topic 2] [adverb] [amount] [verb + nuance].

That is a very normal Japanese pattern: put the context first, then the action at the end of each clause.

No. Standard Japanese is normally written without spaces between words.

So this sentence would usually be written as:

母はいつもより早く私を起こしたが、私はまた少し昼寝してしまった。

Spaces are sometimes added in learning materials to help beginners see word boundaries, but they are not normally used in ordinary Japanese writing.