Besok malam, kakak perempuan saya masuk shift malam di rumah sakit.

In Indonesian, time expressions are very often placed at the beginning of the sentence to set the time frame first.

So:

Besok malam, kakak perempuan saya masuk shift malam di rumah sakit.

feels very natural, like:

Tomorrow night, my older sister works the night shift at the hospital.

You could also say:

Kakak perempuan saya masuk shift malam di rumah sakit besok malam.

That is still grammatical, but starting with the time phrase is very common.

Besok malam means tomorrow night or sometimes tomorrow evening, depending on context.

• besok = tomorrow
• malam = night / evening

Indonesian time words do not always divide the day exactly the same way English does, so malam can cover what English might call evening or night.

Because the two instances of malam do different jobs:

• besok malam = the time when this happens (tomorrow night)
• shift malam = the kind of shift (night shift)

So the sentence is not repetitive in a bad way. It is simply saying:

• when? tomorrow night
• what shift? the night shift

Kakak means older sibling, but by itself it does not always specify gender.

So:

• kakak saya = my older sibling / my older brother / my older sister
• kakak perempuan saya = my older sister

Adding perempuan makes it clear that the older sibling is female.

In everyday speech, if the gender is already understood, many people would just say kakak saya.

They are not the same.

• kakak perempuan = older sister
• saudara perempuan = sister / female sibling, usually more formal or less specific about age

Indonesian often distinguishes siblings by age:

• kakak = older sibling
• adik = younger sibling

So if you specifically mean older sister, kakak perempuan is the better choice.

Because Indonesian possessives usually come after the noun.

So:

• kakak perempuan saya = literally older sister female my
• natural English = my older sister

This is a very common pattern:

• rumah saya = my house
• ibu saya = my mother
• teman saya = my friend

So the order is:

noun + possessive

not

possessive + noun as in English.

Yes, masuk often means to enter or to go in, but in this sentence it has a more idiomatic work-related meaning.

Here, masuk shift malam means something like:

• to start the night shift
• to be on the night shift
• to go in for the night shift

In Indonesian, masuk is commonly used in work and school contexts:

• masuk kerja = go to work / start work
• masuk sekolah = attend school / start school
• masuk shift malam = start the night shift

So this is a very natural usage, even though the basic meaning of masuk is enter.

Because shift is a common borrowed word in Indonesian, especially in workplace contexts.

So shift malam is very normal Indonesian for night shift.

Borrowed English words are very common in modern Indonesian, especially in areas like:

• work
• business
• technology
• medicine

Depending on context, you might also hear other expressions, but shift malam is very common and natural.

Indonesian often does not mark the future with a special word if the time is already clear from context.

Here, besok malam already tells you the event is in the future, so no extra future marker is necessary.

English often needs something like:

• will
• is going to

Indonesian usually does not.

You could add a future marker like akan, but it is not necessary here:

• Besok malam, kakak perempuan saya akan masuk shift malam di rumah sakit.

That is also correct, but slightly more explicit.

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

• di rumah sakit = at the hospital
• ke rumah sakit = to the hospital

In this sentence, the hospital is the place where she works the shift, so di is the right choice.

If you wanted to emphasize going there, you might say something different, such as:

• Besok malam, kakak perempuan saya pergi ke rumah sakit.
  = Tomorrow night, my older sister goes to the hospital.

But that would not specifically mean that she is working the night shift.

Because Indonesian does not have articles that work like English a/an/the.

So:

• di rumah sakit can mean at the hospital or at a hospital, depending on context.

The context usually makes it clear.

This is normal in Indonesian:

• saya di kantor = I’m at the office
• dia di sekolah = she is at school
• mereka di rumah sakit = they are at the hospital

The comma separates the fronted time expression from the rest of the sentence.

So:

Besok malam, kakak perempuan saya masuk shift malam di rumah sakit.

The comma helps readability, especially in writing.

In informal writing, people may leave it out:

Besok malam kakak perempuan saya masuk shift malam di rumah sakit.

That is still understandable. The comma is mainly a punctuation choice that makes the sentence clearer.