hayaku sitaku wo sureba, matiawase no zikan ni maniaimasu.

Because 早く is the adverb form of 早い.

• 早い = early / fast
• 早く = early / quickly

Here, it modifies the verb 支度をする (to get ready / prepare), so you need the adverb:

• 早く支度をする = to get ready quickly

This is like changing an adjective into something that can describe how an action is done.

支度（したく） means preparation or getting ready.

In this sentence, 支度をする is a very common expression meaning:

• to get ready
• to prepare

So:

• 早く支度をすれば = if you get ready quickly

It is often used for everyday preparation, such as getting ready to leave the house, getting dressed, or preparing for something.

Because 支度する can also be expressed as 支度をする.

Here, 支度 is treated like a noun, and する is the verb to do:

• 支度 = preparation
• 支度をする = to do preparation / to get ready

So the を marks 支度 as the thing being done.

Both 支度する and 支度をする are used, but 支度をする is very common in everyday Japanese.

すれば is the conditional ba-form of する.

Formation:

• する → すれば

It means if (someone) does.

So:

• 支度をすれば = if (you) get ready

In this sentence, it combines with 早く:

• 早く支度をすれば = if you get ready quickly

～ば expresses a condition: if... then...

So the sentence structure is:

• 早く支度をすれば、 if you get ready quickly,
• 待ち合わせの時間に間に合います。 you will make it in time for the meeting time.

The ～ば conditional often sounds a little neutral, logical, or matter-of-fact.

Both can often be translated as if, but they are not always identical.

In this sentence:

• 早く支度をすれば = if you get ready quickly
• 早く支度をしたら = also possible, and often very natural in conversation

A rough difference:

• ～ば can sound a bit more general or logical
• ～たら often sounds more conversational and situation-based

So this sentence with すれば feels like:

• If you get ready quickly, then you'll make it in time

With したら, it might feel slightly more like practical advice in conversation.

The subject is omitted, which is very common in Japanese.

From context, the implied subject is probably you:

• (あなたが) 早く支度をすれば、待ち合わせの時間に間に合います。

Japanese often leaves out subjects when they are obvious from the situation.

So even though English usually needs you, Japanese does not.

待ち合わせ（まちあわせ） means meeting up with someone, an arranged meeting, or a meetup.

It refers to a situation where people agree beforehand to meet at a certain place and time.

So:

• 待ち合わせの時間 = the time of the meetup / the agreed meeting time

This is different from a formal business meeting. It is more like:

• meeting a friend
• meeting someone at the station
• rendezvous / meetup time

The の connects two nouns.

• 待ち合わせ = meetup / meeting arrangement
• 時間 = time

So:

• 待ち合わせの時間 = the time for the meetup
• more literally: the meetup’s time

This is a very common noun-linking pattern in Japanese.

Here, に marks the target point that someone makes it by or for.

With 間に合う, に is commonly used for the deadline or target time:

• 時間に間に合う = to make it in time
• 6時に間に合う = to make it by 6:00

So:

• 待ち合わせの時間に間に合います = you will make it in time for the meeting time

間に合う（まにあう） means:

• to be in time
• to make it in time
• to be enough / to suffice (in other contexts)

In this sentence, it has the time-related meaning:

• 待ち合わせの時間に間に合います = you’ll make it in time for the meetup

The dictionary form is 間に合う. 間に合います is the polite form.

This is normal in Japanese.

When a sentence ends politely, earlier parts of the sentence do not also have to be polite. Only the final verb usually determines the politeness level of the whole sentence.

So this pattern is very common:

• subordinate clause: plain form
• sentence ending: polite form

Example pattern:

• 雨が降れば、行きません。
• If it rains, I won’t go.

So すれば + 間に合います is perfectly natural.

Here it most naturally means quickly.

That is because it modifies 支度をする (to get ready), so the idea is:

• get ready quickly

If you translated it as early, the meaning would still be somewhat understandable, but quickly is the more natural reading in this sentence.

Yes, it is natural and understandable.

It means you will make it by the scheduled meetup time.

You may also hear slightly different expressions, such as:

• 待ち合わせに間に合う = make it in time for the meetup
• 待ち合わせの時間に間に合う = make it in time for the meetup time

The version in your sentence is a bit more explicit because it specifically mentions the time.

The comma marks a pause between the if-clause and the main result clause.

• 早く支度をすれば、 = If you get ready quickly,
• 待ち合わせの時間に間に合います。 = you’ll make it in time for the meetup.

Japanese commas are sometimes more flexible than English commas, so you may see sentences like this with or without one. Here it helps readability.

Yes.

Depending on context, it can sound like:

• a neutral statement of consequence
• practical advice
• a mild suggestion

For example, someone might say this to encourage another person to hurry:

• 早く支度をすれば、待ち合わせの時間に間に合います。
• If you get ready quickly, you’ll make it in time for the meetup.

It is not a command, but it can function as gentle advice.