Learn Hardcore Indonesian: Kami melaporkan masalah itu kepada polisi.

me-: a verb-forming prefix (often marks an active verb).
-kan: a suffix that often makes the verb transitive (taking a direct object), and can add a sense of “doing something to/for someone/something”.

Roughly:

lapor = (to) report (more basic, often in dictionaries, informal speech)
melapor = to report (intransitive / not followed by an object)
melaporkan [something] = to report something (explicit object)

In this sentence:

melaporkan masalah itu = to report that problem.

So melaporkan is used because it takes masalah itu as its direct object.

Why is it masalah itu and not itu masalah? What is the difference?

In Indonesian, demonstratives like ini (this) and itu (that) usually come after the noun:

masalah itu = that problem / the problem
masalah ini = this problem

So:

masalah itu is the normal, neutral way to say that problem.

itu masalah also exists but means something different:

itu masalah = that is a problem (a whole sentence: itu = that, masalah = (a) problem)

So:

Kami melaporkan masalah itu = We reported that problem.
Itu masalah = That is a problem. (Different structure, different meaning.)

Does masalah itu mean “that problem” or “the problem”? How definite is it?

masalah itu can be translated as either that problem or the problem depending on context.

When contrast or distance is emphasized: that problem.
When the problem is already known to both speaker and listener: often translated as the problem in natural English.

Indonesian does not have separate words for a/the like English, so itu often signals that the noun is specific/known/previously mentioned, which frequently matches the or that in English.

Why do we use kepada before polisi? Could we say ke polisi or pada polisi instead?

kepada is often used when something is directed to a person or party (recipient), especially in more formal or careful language.

melaporkan masalah itu kepada polisi
= report the problem to the police (police as the recipient of the report)

Alternatives:

ke polisi: also used in everyday speech, sounds a bit more casual.
Kami melaporkan masalah itu ke polisi is very common in conversation.
pada polisi: possible but sounds more formal/literary or a bit stiff in this sentence; kepada is more natural.

So:

Formal / standard: kepada polisi
Colloquial / common: ke polisi

Can we change the word order, like Kami melaporkan kepada polisi masalah itu?

Yes, that word order is grammatically possible, but it sounds less neutral and a bit marked or emphatic.

Kami melaporkan masalah itu kepada polisi.
→ Most natural, neutral order: Subject – Verb – Object – Prepositional phrase.
Kami melaporkan kepada polisi masalah itu.
→ Sounds like you’re emphasizing kepada polisi (to the police) first, then specifying which problem. It can be used in speech for emphasis, but it is not the most typical basic pattern.

For learners, it’s safer and more natural to stick with:

Kami melaporkan masalah itu kepada polisi.

How do we know this sentence is in the past (reported), when there is no tense marker?

Indonesian verbs do not change form for tense (past/present/future). melaporkan itself is tense-neutral.

The time is understood from:

Context, or
Time expressions like tadi (earlier), kemarin (yesterday), nanti (later), etc.

So:

Kami melaporkan masalah itu kepada polisi.
Could mean:
- We reported that problem to the police (past),
- We are reporting that problem to the police (present, depending on context),
- less commonly, We will report that problem to the police (future), if clearly supported by context.

To make it clearly past, people often add time words:

Tadi kami melaporkan masalah itu kepada polisi. (Earlier, we reported…)
Kemarin kami melaporkan masalah itu kepada polisi. (Yesterday, we reported…)

Can we drop kami and just say Melaporkan masalah itu kepada polisi?

In standard sentences, Indonesian usually still includes the subject pronoun, especially in writing and in clear, complete sentences.

Kami melaporkan masalah itu kepada polisi.
→ Full, natural sentence.

Melaporkan masalah itu kepada polisi without kami:

Could appear as a fragment (e.g., in a note, heading, or instruction),
Or in very informal speech when the subject is obvious from context.

But as a normal sentence, it sounds incomplete; the listener may wonder who reported it. For learners, it is better to keep kami (or the appropriate subject) in place.

Is polisi singular or plural here? Does it mean “the police (as an institution)” or “a police officer”?

Indonesian polisi can mean:

The police as an institution:
- Kami melaporkan masalah itu kepada polisi.
  = We reported the problem to the police (the authorities).
A police officer (especially in informal speech):
- Saya bertanya kepada polisi.
  = I asked a police officer.

The sentence Kami melaporkan masalah itu kepada polisi is most naturally understood as reporting to the police (institution) unless context clearly points to an individual officer.

Indonesian doesn’t mark singular/plural on the noun here, so English translation chooses based on context.

Can we use tersebut instead of itu, as in masalah tersebut? What is the difference?

Yes, you can say:

Kami melaporkan masalah tersebut kepada polisi.

tersebut is more formal and often used in written language (news reports, official documents). It means roughly the aforementioned or that (previously mentioned).

Nuance:

masalah itu: that problem / the problem (neutral, everyday)
masalah tersebut: that (specific/aforementioned) problem (more formal, often in reports/news)

Both are correct; itu is more general and common in conversation, tersebut sounds more formal or report-like.