Saya harus menunggu lebih lama di stasiun karena kereta terlambat.

Yes, aku could also be used, but saya is more neutral and polite.

• saya = standard, polite, safe in most situations
• aku = more casual and personal

So:

• Saya harus menunggu... sounds neutral/polite.
• Aku harus menunggu... sounds more informal.

Harus expresses necessity or obligation. In English, it can correspond to must, have to, or sometimes need to, depending on context.

In this sentence, it means something like had to / have to wait longer.

A useful point: harus does not change form. Indonesian verbs and modals do not conjugate for person the way English does.

• Saya harus
• Dia harus
• Mereka harus

All use the same harus.

Menunggu is the normal active verb form in a regular statement.

It comes from the base/root tunggu. The prefix meN- creates the active verb:

• tunggu = wait / the root
• menunggu = to wait, to be waiting

In everyday Indonesian, bare roots like tunggu often appear in:

• commands: Tunggu! = Wait!
• very casual speech
• certain shortened styles

But in a standard sentence like this, menunggu is the expected form.

Indonesian menunggu already includes the idea of wait for, so you usually do not need a separate preposition.

For example:

• Saya menunggu kereta. = I am waiting for the train.

In your sentence, there is no direct object after menunggu. Instead, the sentence tells us:

• how long: lebih lama
• where: di stasiun
• why: karena kereta terlambat

So menunggu does not need a separate word meaning for.

Lebih lama means longer or for a longer time.

• lama = long in duration
• lebih = more

So together:

• lebih lama = longer

This is about time, not physical size.

Because lama is used for duration of time, while panjang is used for physical length.

• menunggu lebih lama = wait longer
• jalan lebih panjang = a longer road

So in this sentence, lama is the correct word because the speaker is talking about how much time they had to wait.

That is the most natural position. It modifies the action of waiting:

• menunggu lebih lama = wait longer

Indonesian commonly puts this kind of modifier after the verb.

You may hear other word orders for emphasis, but Saya harus menunggu lebih lama... is the most neutral and natural version.

Because di marks a location, while ke marks movement toward a destination.

• di stasiun = at the station
• ke stasiun = to the station

In this sentence, the speaker is already describing the place where the waiting happened, so di stasiun is correct.

Indonesian often does not use a verb equivalent to is/was when the predicate is an adjective.

So:

• kereta terlambat = the train is late / was late

There is no need for adalah here. In fact, adalah would usually sound unnatural in this kind of sentence.

This is very common in Indonesian:

• Saya lelah = I am tired
• Cuacanya panas = The weather is hot
• Kereta terlambat = The train is late

This is an important distinction.

• lambat = slow
• terlambat = late, delayed, too late

So:

• kereta lambat would mean a slow train
• kereta terlambat means the train is late

In your sentence, the intended idea is clearly late/delayed, so terlambat is the right choice.

Not by itself. Indonesian does not mark tense the way English does.

So Saya harus menunggu lebih lama di stasiun karena kereta terlambat could refer to:

• a past situation
• a present situation
• sometimes even a future situation, depending on context

Time is usually understood from context or from time words such as:

• kemarin = yesterday
• tadi = earlier
• sekarang = now
• besok = tomorrow

So Indonesian relies heavily on context rather than verb endings.

Karena means because and introduces the reason.

Yes, the clause order can be changed. Both are correct:

• Saya harus menunggu lebih lama di stasiun karena kereta terlambat.
• Karena kereta terlambat, saya harus menunggu lebih lama di stasiun.

The first version is often more natural in ordinary conversation, but both are fine.

Indonesian generally does not use articles like a, an, or the.

So:

• stasiun can mean a station or the station
• kereta can mean a train or the train

The exact meaning is usually understood from context.

That is why the sentence does not need extra words corresponding to English articles.

In many everyday contexts, kereta is enough and is commonly understood as train.

Kereta api is the fuller, more explicit term for train, and you may see it in more formal writing or when clarity is needed.

So both can work, but in natural everyday speech, kereta is very common.