Saya heran kenapa dia belum membalas pesan saya.

Yes. Saya heran literally means I am surprised or I find it strange.

In this sentence, heran expresses a feeling of puzzlement or surprise. Depending on context, Saya heran kenapa... can sound like:

• I’m surprised that...
• I wonder why...
• I find it strange that...

So heran is not just shock or amazement; it often means something feels odd or unexpected.

Kenapa means why.

In Indonesian, it is very common to put kenapa after verbs of thinking, knowing, asking, wondering, or being surprised, such as:

• Saya tahu kenapa... = I know why...
• Dia tanya kenapa... = He/She asked why...
• Saya heran kenapa... = I’m surprised why... / I wonder why...

So the structure is very natural:

• Saya heran = I’m surprised
• kenapa dia belum membalas pesan saya = why he/she has not replied to my message

Yes. Mengapa and kenapa both mean why.

The main difference is tone:

• kenapa = more common in everyday speech
• mengapa = a bit more formal or written

So these are both correct:

• Saya heran kenapa dia belum membalas pesan saya.
• Saya heran mengapa dia belum membalas pesan saya.

For normal conversation, kenapa is usually the more natural choice.

Belum means not yet.

That is different from tidak, which means not.

Compare:

• Dia belum membalas pesan saya. = He/She has not replied yet.
• Dia tidak membalas pesan saya. = He/She did not reply / does not reply.

So belum suggests the action may still happen later. It leaves the possibility open.

That is why belum fits well here: the speaker is wondering why the person still hasn’t replied yet.

Membalas is the active verb form of balas.

• balas = reply, return, answer back, repay
• membalas = to reply / to answer / to respond

In Indonesian, many verbs take the prefix meN- to form an active verb. Here:

• balas → membalas

In the sentence, membalas pesan means to reply to a message.

So:

• dia belum membalas pesan saya = he/she hasn’t replied to my message yet

Both can be understood, but membalas pesan is especially common for replying to a message, text, chat, email, or comment.

Useful distinction:

• menjawab = to answer
• membalas = to reply / respond back

Examples:

• menjawab pertanyaan = answer a question
• membalas pesan = reply to a message
• membalas email = reply to an email

So in this sentence, membalas pesan is very natural.

Because the first saya is the subject, and the second saya shows possession.

Breakdown:

• Saya = I
• pesan saya = my message

So the sentence literally contains:

• I am surprised
• he/she has not yet replied to my message

Repeating saya is completely normal in Indonesian. It does not sound awkward the way too much repetition sometimes can in English.

Yes. Both are correct.

• pesan saya = my message
• pesanku = my message

The difference is mostly style and register:

• pesan saya sounds a bit more neutral or formal
• pesanku sounds a bit more personal, casual, and natural in speech

So a more casual version might be:

• Aku heran kenapa dia belum membalas pesanku.

Both are good; it depends on the tone you want.

Yes, dia can mean either he or she.

Indonesian does not usually mark gender in third-person singular pronouns. So:

• dia = he / she

You understand the gender only from context, if it matters at all.

That means the sentence could refer to either a man or a woman.

Indonesian often does not need an extra word like that where English might use one.

The sentence moves directly from:

• Saya heran = I’m surprised to
• kenapa dia belum membalas pesan saya = why he/she hasn’t replied to my message yet

This is normal Indonesian structure.

Sometimes Indonesian uses bahwa for that, but not usually before kenapa in a sentence like this.

So Saya heran kenapa... is the natural pattern.

Yes, it is fairly straightforward.

Break it down:

• kenapa = why
• dia = he/she
• belum = not yet
• membalas = reply
• pesan saya = my message

So Indonesian keeps a simple order:

• why + subject + not yet + verb + object

Unlike English, Indonesian does not need helping verbs like has, does, or did.

English:

• why he hasn’t replied to my message yet

Indonesian:

• kenapa dia belum membalas pesan saya

That makes the grammar simpler in some ways.

It depends on the situation.

• saya = neutral, polite, standard
• aku = casual, personal, informal

So:

• Saya heran kenapa dia belum membalas pesan saya.
  sounds neutral and polite

• Aku heran kenapa dia belum membalas pesanku.
  sounds more casual and conversational

A native speaker might very naturally say the second one in everyday life, especially with friends.

Yes. In casual spoken Indonesian, people often shorten or relax some words.

For example:

• Aku heran kenapa dia belum bales pesanku.
• Aku heran kok dia belum bales pesanku.

Notes:

• membalas → bales in casual speech
• pesan saya → pesanku
• kok can add a feeling like how come or why is it that

So the original sentence is correct and natural, but it sounds a bit more standard than very casual everyday speech.

Yes, very often.

Even though heran literally relates to surprise, in real use Saya heran kenapa... can sound close to:

• I wonder why...
• I don’t understand why...
• It’s strange that...

The exact nuance depends on tone:

• If said calmly, it may mean simple curiosity.
• If said with emotion, it can show annoyance, confusion, or disappointment.

So this structure is quite flexible in real conversation.