Kalau yogurt dan sereal sudah dibayar, tinggal simpan struknya di tas.

Kalau means if here.

So Kalau yogurt dan sereal sudah dibayar ... means If the yogurt and cereal have already been paid for ...

In everyday Indonesian, kalau is very common in speech and informal writing. In some contexts it can also feel like when if the speaker assumes the condition will happen, but if is the safest translation here.

A more formal alternative is jika, but kalau sounds very natural in conversation.

Because dibayar is a passive form, while membayar is an active form.

• membayar = to pay, to pay for something
• dibayar = to be paid, to be paid for

So:

• yogurt dan sereal sudah dibayar = the yogurt and cereal have already been paid for

If you used membayar, the yogurt and cereal would sound like the ones doing the paying, which makes no sense.

This is a very common Indonesian pattern:

• Buku itu sudah dibeli. = The book has already been bought.
• Makanannya sudah dimasak. = The food has already been cooked.

Indonesian often leaves out the agent when it is obvious, unimportant, or not the focus.

In sudah dibayar, the important point is simply that the items are already paid for. The sentence does not need to say who paid.

English does this too:

• It’s already been paid for.

If you wanted to mention the person in Indonesian, you could say:

• Kalau yogurt dan sereal sudah dibayar oleh Ibu, ... = If the yogurt and cereal have already been paid for by Mom, ...
• Kalau saya sudah membayar yogurt dan sereal, ... = If I have already paid for the yogurt and cereal, ...

But the original sentence sounds natural because the doer is not important.

Sudah shows that something is already completed.

So:

• dibayar = paid
• sudah dibayar = already paid / has been paid

It gives the idea of completion before the next action happens.

In this sentence, the sequence is:

1. the yogurt and cereal are paid for
2. then you just keep the receipt in the bag

Without sudah, the sentence would sound less clearly completed.

Yes, tinggal can mean to live/stay, but in this sentence it has a different meaning.

Here, tinggal + verb means:

• just
• only need to
• all that remains is to

So tinggal simpan struknya di tas means something like:

• just keep the receipt in the bag
• then all you need to do is put the receipt in the bag

This is a very common structure:

• Tinggal klik tombol ini. = You just need to click this button.
• Tinggal tunggu hasilnya. = Now you just wait for the result.

So this is not the live/stay meaning of tinggal.

Because Indonesian often omits the subject when it is understood from context, especially in:

• instructions
• reminders
• casual conversation

So tinggal simpan struknya di tas is like saying:

• just put the receipt in the bag
• just keep the receipt in your bag

The implied subject is something like you, but Indonesian does not need to say it.

If you wanted to make it explicit, you could say:

• ... tinggal kamu simpan struknya di tas.
• ... tinggal simpan saja struknya di tas.

But the original version is very natural.

Struk means receipt.

The ending -nya here makes it sound like:

• the receipt
• the receipt for it
• its receipt

In this sentence, struknya most naturally means the receipt connected with that purchase.

The suffix -nya does not always mean his/her/its in a strict possessive sense. Very often it makes a noun more definite or specific.

So:

• struk = a receipt
• struknya = the receipt / its receipt / that receipt

This use of -nya is extremely common in Indonesian.

Di marks a location, while ke marks movement toward a destination.

Here, simpan ... di tas is a very natural expression meaning:

• store it in the bag
• keep it in the bag

Even though English might say put it into the bag, Indonesian often uses simpan di tas because the final location matters more than the movement.

Compare:

• Simpan struknya di tas. = Keep the receipt in the bag.
• Masukkan struknya ke tas. = Put the receipt into the bag.

Both can work, but they focus slightly differently:

• simpan di tas = keep/store in the bag
• masukkan ke tas = put into the bag

They are similar, but not identical.

• simpan = keep/store/put away
• taruh = put/place
• letakkan = place/put, often a bit more neutral or formal

In this sentence, simpan is a good choice because the idea is not just placing the receipt for a second, but keeping it there.

So:

• Simpan struknya di tas = Keep the receipt in the bag
• Taruh struknya di tas = Put the receipt in the bag
• Letakkan struknya di tas = Place the receipt in the bag

All are possible, but simpan best matches the idea of keeping it safely.

Yes. They are common Indonesian words borrowed from English and other languages.

• yogurt = yogurt
• sereal = cereal

This kind of borrowing is very common in Indonesian, especially for food, technology, and modern everyday items.

The spelling may differ slightly from English in some borrowed words, but here both are standard and easy to recognize.

Yes. The original sentence sounds natural and conversational. More formal or alternative versions could be:

• Jika yogurt dan sereal sudah dibayar, simpan saja struknya di tas.
• Kalau yogurt dan serealnya sudah dibayar, struknya tinggal disimpan di tas.
• Setelah yogurt dan sereal dibayar, struknya disimpan di tas.

These versions differ a little in tone:

• kalau = conversational
• jika = more formal
• tinggal simpan = very natural, spoken-like, efficient
• tinggal disimpan = more passive and slightly more formal

So the original sentence is a good example of everyday Indonesian.