Saya heran kenapa dia diam-diam membawa novel itu ke kelas tanpa memberi tahu siapa pun.

Yes, saya heran literally means I am surprised or I am puzzled. In this sentence, it is very natural to translate it as I wonder or I’m puzzled.

So:

• Saya heran = I’m surprised / puzzled / I wonder
• Saya heran kenapa... = I wonder why...

In Indonesian, heran often expresses puzzlement, not only shock.

Yes. Kenapa and mengapa both mean why.

The difference is mainly tone and style:

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

So this sentence could also be:

• Saya heran mengapa dia diam-diam membawa novel itu ke kelas tanpa memberi tahu siapa pun.

That would mean the same thing, just with a slightly more formal feel.

Because Indonesian often does not need an equivalent of that in this kind of sentence.

English:

• I’m surprised that he...
• I wonder why he...

Indonesian can go straight into the clause:

• Saya heran kenapa dia...

Here, kenapa already introduces the idea of why, so no extra connector is needed.

It can mean either one. Dia is gender-neutral.

So depending on context, this sentence could mean:

• I wonder why he secretly brought that novel to class...
• I wonder why she secretly brought that novel to class...

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

Yes. Diam means silent, quiet, or still. But diam-diam is a fixed expression meaning:

• secretly
• quietly
• without others knowing

So in this sentence:

• diam-diam membawa = secretly brought

It does not just mean the person was physically quiet while carrying the novel. It means they did it in secret.

Yes. Diam-diam is a reduplicated form.

In Indonesian, reduplication can do different things depending on the word. Here, it creates an adverbial expression with a special meaning. It is best learned as a set phrase:

• diam = silent / quiet
• diam-diam = secretly

So this is not just a simple plural or repeated version of diam. It has its own idiomatic meaning.

Because in Indonesian, demonstratives like ini and itu usually come after the noun.

So:

• novel itu = that novel
• kelas itu = that class / that classroom
• orang itu = that person

This is one of the big differences from English, where that comes before the noun.

It can mean either, depending on perspective. It basically means to bring / carry / take along.

In this sentence:

• membawa novel itu ke kelas = to bring/take that novel to class

English chooses bring or take depending on the speaker’s point of view, but Indonesian membawa is less tied to that distinction.

Because ke shows movement to a place, while di shows location in/at a place.

• ke kelas = to class / to the classroom
• di kelas = in class / in the classroom

Since the person is carrying the novel toward that place, ke is the correct preposition here.

Tanpa memberi tahu means without informing or without telling.

Breakdown:

• tanpa = without
• memberi tahu = to inform / to tell

Memberi tahu is commonly written as two words because it comes from the phrase beri tahu. So:

• memberi tahu seseorang = to tell someone
• tanpa memberi tahu = without telling

This is a very common expression in Indonesian.

Because siapa pun is the object here.

The structure is:

• tanpa memberi tahu siapa pun
• literally: without informing anyone

So siapa pun is receiving the action of memberi tahu.

Here it means anyone.

So:

• tanpa memberi tahu siapa pun = without telling anyone

In other contexts, siapa pun can sometimes mean whoever, but in this sentence it clearly means anyone.

In standard Indonesian, siapa pun is written separately when pun functions like this.

So:

• siapa pun = anyone / whoever
• apa pun = anything / whatever

Learners often see forms written together online, but the standard spelling is usually separate in cases like this.

Yes, it is the same idea.

In:

• dia diam-diam membawa novel itu ke kelas tanpa memberi tahu siapa pun

the understood subject of memberi tahu is still dia.

So the sentence means:

• He/She secretly brought that novel to class without telling anyone

Indonesian often leaves the subject unstated in a subordinate phrase when it is obviously the same as the main subject.

Yes, it is very natural.

The structure is:

• Saya heran = main clause
• kenapa dia diam-diam membawa novel itu ke kelas = embedded why clause
• tanpa memberi tahu siapa pun = additional phrase explaining how/under what circumstances

It flows naturally in Indonesian and sounds like normal written or spoken language.

Yes, sometimes adverbs can move a little, but the current position is very natural.

For example:

• Saya heran kenapa dia diam-diam membawa novel itu ke kelas...
• Saya heran kenapa dia membawa novel itu ke kelas diam-diam...

The first version sounds more natural. Putting diam-diam before membawa clearly shows that it describes the action of bringing the novel secretly.

It could mean either one depending on context.

• ke kelas can mean to class
• It can also mean to the classroom

Indonesian kelas often covers both the lesson/class session and the physical classroom, so English translation depends on the situation.