asita made ni owaru ka douka, watasi ha mada wakarimasen.

までに means by / by the time of and marks a deadline.

• 明日までに終わる = to finish by tomorrow
• It focuses on the latest point in time when something will be completed.

By contrast, まで by itself often means until.

Compare:

• 明日までに終わる = it will be finished by tomorrow
• 明日まで待つ = wait until tomorrow

So in this sentence, 明日までに is setting a deadline, not a duration.

Because this clause is embedded inside a larger sentence.

In Japanese, when a verb comes before かどうか, it is normally in the plain form:

• 終わるかどうか
• 行くかどうか
• できるかどうか

Using 終わりますかどうか would sound unnatural.

The politeness of the whole sentence is still shown at the end with 分かりません. This is very common in Japanese: subordinate clauses often use plain forms, while the final verb carries the politeness level.

かどうか means whether or not.

So:

• 終わるかどうか = whether it will finish / whether it will be finished

This pattern is used when the speaker does not know if something is true.

Examples:

• 行くかどうか分かりません。 = I don’t know whether I’ll go.
• できるかどうか心配です。 = I’m worried about whether I can do it.

In your sentence, 明日までに終わるかどうか is the whole idea being questioned: whether it will be finished by tomorrow.

Here, か is not making the whole sentence into a direct question. Instead, it is part of the embedded expression かどうか.

Think of it like this:

• direct question: 終わりますか。 = Will it finish?
• embedded question: 終わるかどうか分かりません。 = I don’t know whether it will finish.

So か can appear inside a statement when the speaker is talking about a question or uncertainty.

Yes, it can often be omitted.

Japanese often leaves out subjects when they are clear from context. So this sentence could naturally be said as:

• 明日までに終わるかどうか、まだ分かりません。

That would usually still mean I still don’t know whether it will be finished by tomorrow.

Adding 私は gives a bit more explicit contrast or emphasis, like:

• As for me, I still don’t know
• or possibly contrasting with someone else who does know

So 私は is not always necessary, but it is grammatically fine and can add focus.

まだ here means still.

• まだ分かりません = I still don’t know

It shows that the situation has not changed yet. The speaker may expect that they will know later, but at this moment they do not.

Compare:

• まだ終わっていません。 = It still isn’t finished.
• まだ決めていません。 = I still haven’t decided.

So in your sentence, まだ adds the nuance that the answer is not known yet.

This is a very common learner question.

In Japanese:

• 分かる = to understand / to know in the sense of be aware of the answer
• 知る / 知っている = to know information, facts, or people

With whether or not clauses, Japanese usually uses 分かる:

• 行くかどうか分かりません。
• できるかどうか分かりません。

Using 知りません here would sound unnatural.

A helpful way to think about it:

• 知っている = I possess that information
• 分かる = I can tell / I understand / I know the answer

So まだ分かりません is the natural expression for I still don’t know whether...

The comma separates the embedded clause from the main clause.

• 明日までに終わるかどうか = whether it will be finished by tomorrow
• 私はまだ分かりません = I still don’t know

So the comma helps show the structure:

[whether it will finish by tomorrow], [I still don’t know].

Japanese commas are sometimes more flexible than English commas, so you may also see the sentence written without one. But here it helps readability.

終わる is intransitive: to end / to be finished.
終える is transitive: to finish something.

In this sentence, 終わる is used because the focus is on whether the thing will be finished by the deadline, not on who finishes it.

• 明日までに終わる = it will be finished by tomorrow / it will end by tomorrow

If you wanted to say that someone finishes it, you could use 終える:

• 明日までにそれを終えるかどうか、まだ分かりません。 = I still don’t know whether I will finish it by tomorrow.

So 終わる is perfectly natural when the subject is unstated or the completion itself is the focus.

The structure is:

[embedded clause] + [main clause]

More specifically:

• 明日までに終わるかどうか = whether it will finish by tomorrow
• 私はまだ分かりません = I still don’t know

So the whole sentence is literally something like:

• Whether it will be finished by tomorrow, I still don’t know.

This kind of order is very common in Japanese. The thing that is unknown appears first, and the main verb 分かりません comes at the end.

Yes, that is possible, but the nuance is a little different.

• 終わるかどうか、まだ分かりません explicitly says whether or not
• 終わるか、まだ分かりません is shorter and can also mean I don’t know if it will finish

In many contexts they are very similar. However, かどうか sounds more complete and explicit, especially in careful or standard written/spoken Japanese.

So:

• 終わるか、まだ分かりません = natural, shorter
• 終わるかどうか、まだ分かりません = very clear, standard, and explicit

In this sentence, it naturally modifies 終わる, not 分かりません.

So the meaning is:

• whether it will be finished by tomorrow

not:

• I won’t know by tomorrow

If you wanted to say I still won’t know by tomorrow, you would phrase it differently, for example:

• 明日までにはまだ分からないかもしれません。

So in your original sentence, the deadline applies to the finishing, not to the speaker’s knowing.

Yes. They are the same word.

• 分かりません uses kanji
• わかりません uses hiragana

Both are common. Many textbooks and learners use わかりません because it is easier to read at first, but 分かりません is also very standard.

So this is just a writing difference, not a grammar difference.