Walaupun dulu sering bertengkar, dua sahabat itu sekarang akrab sekali dan selalu akur.

Walaupun means although / even though. It introduces a contrast:

• Walaupun dulu sering bertengkar = Although they often argued in the past
• the rest of the sentence tells you the surprising or contrasting result: dua sahabat itu sekarang akrab sekali dan selalu akur.

Very similar words are meskipun and biarpun. In this sentence, all three would work.

Because the subject is already understood from the main clause: dua sahabat itu.

A fuller version would be:

Walaupun dua sahabat itu dulu sering bertengkar, dua sahabat itu sekarang akrab sekali dan selalu akur.

But repeating the subject would sound unnecessary. Indonesian often leaves out a subject when it is obvious from context.

So the sentence naturally means:

Although those two close friends often argued in the past, they are now very close and always get along.

Dulu means before, back then, or in the past.

In this sentence, it sets the time frame for sering bertengkar:

• dulu sering bertengkar = used to argue often / often argued in the past

It contrasts with sekarang later in the sentence:

• dulu = then / in the past
• sekarang = now

That past-vs-present contrast is an important part of the sentence.

Yes, dulu can move around somewhat because it is a time adverb.

These are all possible:

• Walaupun dulu sering bertengkar, ...
• Walaupun sering bertengkar dulu, ...
• Dulu, walaupun sering bertengkar, ...

But the original version is very natural because dulu appears early and immediately sets the time frame. That makes the contrast with sekarang especially clear.

Bertengkar usually means to argue / quarrel, especially with words.

Berkelahi means to fight physically.

So:

• sering bertengkar = they often argued
• sering berkelahi = they often got into physical fights

For two friends, bertengkar is the normal choice if the idea is disagreement, bickering, or quarrelling.

It means those two close friends or the two close friends.

Breakdown:

• dua = two
• sahabat = close friend, dear friend
• itu = that / those / the (depending on context)

A few useful points:

1. Sahabat is stronger than teman.

   • teman = friend, companion, acquaintance
   • sahabat = close friend / best friend type of relationship

2. In Indonesian, itu comes after the noun phrase:

   • sahabat itu = that friend / the friend
   • dua sahabat itu = those two friends / the two friends

So the word order is normal Indonesian word order.

Because Indonesian demonstratives usually come after the noun, not before it.

Compare:

• English: those two friends
• Indonesian: dua sahabat itu

This pattern is very common:

• buku itu = that book / the book
• orang itu = that person
• rumah besar itu = that big house

So itu follows the whole noun phrase.

Akrab sekali means very close, very friendly, or extremely familiar with each other.

• akrab = close, friendly, familiar
• sekali = very

In Indonesian, sekali as an intensifier usually comes after the adjective:

• bagus sekali = very good
• besar sekali = very big
• akrab sekali = very close

You could also say sangat akrab. Both mean very close, but:

• sangat akrab can sound a bit more neutral or formal
• akrab sekali is very natural and expressive

They are related, but not identical.

• akrab = close, warm, familiar, emotionally close
• akur = harmonious, in agreement, not in conflict, getting along well

So:

• akrab sekali focuses on closeness
• selalu akur focuses on harmony

Using both together gives a fuller picture: they are not only close friends, but they also get along well and do not fight.

That is why the combination sounds natural rather than repetitive.

Selalu means always, so it adds the idea that this harmony is consistent.

• akur = harmonious / getting along
• selalu akur = always get along

Without selalu, the sentence would still make sense:

... sekarang akrab sekali dan akur.

But selalu akur sounds stronger and more natural because it emphasizes an ongoing situation, especially after mentioning that they used to argue often.

Yes. Sekarang is fairly flexible.

The original:

Dua sahabat itu sekarang akrab sekali dan selalu akur.

Other possible versions:

• Sekarang dua sahabat itu akrab sekali dan selalu akur.
• Dua sahabat itu akrab sekali dan selalu akur sekarang.

The original version is very natural because sekarang comes right after the subject and clearly marks the present-time contrast with dulu.

Yes:

Walaupun dua sahabat itu dulu sering bertengkar, dua sahabat itu sekarang akrab sekali dan selalu akur.

This is grammatically correct, but it sounds more repetitive. Indonesian often omits information that is already clear.

A very natural alternative would be:

Walaupun dulu sering bertengkar, sekarang dua sahabat itu akrab sekali dan selalu akur.

So the original sentence is concise and idiomatic.

Because walaupun dulu sering bertengkar is an introductory subordinate clause, and the comma separates it from the main clause.

Structure:

• subordinate clause: Walaupun dulu sering bertengkar
• main clause: dua sahabat itu sekarang akrab sekali dan selalu akur

This is similar to English punctuation in sentences like:

Although they used to argue a lot, they are now very close and always get along.

In informal Indonesian, commas are sometimes used loosely, but in a sentence like this, the comma is standard and helpful.