Kalau stok di toko kampus habis, Mbak penjual biasanya menyuruh kami memesan merek lain lewat aplikasi.

Here kalau introduces a condition, so if is the best match.

• Kalau stok di toko kampus habis... = If the stock at the campus store runs out...
• In everyday Indonesian, kalau can sometimes feel a bit like when if the situation is expected to happen, but grammatically it is still a conditional word.

A few similar words:

• kalau = if
• jika = if, more formal
• bila = if, also more formal/literary

Yes. Habis literally means something like finished, used up, or gone.

In this sentence, stok ... habis means the item is out of stock or the stock has run out.

Common uses of habis:

• Uangnya habis = The money is gone / used up
• Makanannya habis = The food is finished
• Stoknya habis = The stock is gone / out of stock

So habis is very common in Indonesian for the idea of something no longer being available.

No. This di is a preposition, not the passive prefix.

• di toko kampus = at/in the campus store
• It is written separately because it is a preposition of location.

Compare:

• di toko = at the store
• dibeli = bought

A useful rule:

• di
  • place/location → written separately
• di-
  • verb in passive form → written together

So here di toko kampus is purely about location.

Yes, literally it is store campus, but this is a normal Indonesian noun pattern.

Indonesian often puts the main noun first and the describing noun second:

• toko kampus = campus store
• buku bahasa = language book
• kantin sekolah = school canteen

So toko kampus is a compact way to say the store associated with the campus.

Depending on context, you might also hear:

• toko di kampus = a store on campus
• toko kampus = the campus store / campus shop

The version in your sentence sounds like a specific store connected with the campus.

Mbak is a polite form of address for a young woman or an adult woman who is not much older than the speaker. It is especially common in Java, but widely understood elsewhere too.

In this sentence, Mbak penjual means something like:

• the saleswoman
• the shop lady
• the female clerk

It adds politeness and sounds natural in everyday Indonesian.

A few related terms:

• Mbak = polite address for a young woman
• Mas = polite address for a young man
• Ibu = Mrs./ma’am, usually for an older woman or in more formal situations
• Bapak/Pak = Mr./sir

Adding Mbak makes the phrase more personal and natural. Penjual by itself just means seller or vendor, but Mbak penjual identifies her as the female shop worker in a polite, everyday way.

So:

• penjual = seller
• Mbak penjual = the female seller / the shop lady

In real conversation, Indonesians often combine a title like Mbak with a role:

• Mbak kasir = the cashier
• Mas barista = the barista
• Pak satpam = the security guard

It is very common spoken Indonesian.

Because biasanya is an adverb meaning usually, and in Indonesian adverbs like this often come before the verb they modify.

So:

• Mbak penjual biasanya menyuruh kami... = The seller usually tells us...

This placement is very normal.

You may also see slightly different placements depending on emphasis, but this one is standard and natural.

Menyuruh means to tell someone to do something, to instruct, or sometimes to order.

In this sentence, it means the seller tells the speakers to order a different brand.

Pattern:

• menyuruh + person + verb

So:

• menyuruh kami memesan = tells us to order

The exact English translation depends on tone:

• tell
• ask
• instruct
• have someone do something

It is stronger than a gentle suggestion, but not always as harsh as order.

This is a very common Indonesian pattern.

Structure:

• menyuruh = tell/instruct
• kami = us
• memesan = to order

So the structure is:

• [someone] tells [someone else] to [do something]

Indonesian does not need a separate word like English to here.

Compare:

• Dia menyuruh saya datang. = He told me to come.
• Ibu menyuruh kami belajar. = Mom told us to study.

So menyuruh kami memesan is perfectly normal and means tells us to order.

Pesan is the root word. Memesan is the active verb form built from it.

• pesan can mean order or message, depending on context
• memesan clearly means to order

So:

• memesan makanan = to order food
• memesan tiket = to book/order tickets

In everyday spoken Indonesian, people sometimes use the shorter root form in places where formal grammar would prefer memesan, but memesan is the standard and clear form here.

Because kami means we/us, but not including the listener.

Indonesian distinguishes between:

• kami = we/us, excluding the person being spoken to
• kita = we/us, including the person being spoken to

In this sentence, kami refers to the group that the seller tells to place the order. It does not include the seller, and probably does not include the person being addressed either.

So kami is the correct choice.

It can mean either another brand or a different brand, depending on context.

• merek = brand
• lain = other, another, different

So memesan merek lain means ordering some other brand instead of the one that is unavailable.

A few examples:

• coba merek lain = try another brand
• warna lain = another color / a different color
• pilihan lain = another option

Yes. Lewat aplikasi means through the app or via the app.

• lewat is very common in everyday speech and writing
• melalui means essentially the same thing, but sounds a bit more formal

So both work:

• lewat aplikasi = via the app
• melalui aplikasi = through the app

In casual everyday Indonesian, lewat is extremely natural.

It is mostly neutral everyday Indonesian.

Why:

• stok is a common everyday word
• Mbak is conversational and polite
• lewat aplikasi sounds natural and modern
• the grammar itself is standard

So it is not highly formal, but it is also not slangy. It sounds like normal spoken or informal written Indonesian.

Yes. A useful breakdown is:

• Kalau stok di toko kampus habis,

  • if the stock at the campus store runs out

• Mbak penjual biasanya menyuruh kami

  • the saleswoman usually tells us

• memesan merek lain

  • to order another/different brand

• lewat aplikasi

  • through the app

So the full structure is:

Condition + main clause + action to be done

That is a very common Indonesian sentence pattern.