Biarpun dia bukan teman lama saya, saya mulai mempercayainya karena dia selalu menepati janji.

Biarpun means although, even though, or even if in many contexts.

In this sentence, Biarpun dia bukan teman lama saya... means Although he/she is not an old/long-time friend of mine...

For many everyday purposes, biarpun, walaupun, and meskipun are very similar and often interchangeable.

A rough sense of style:

• biarpun = common and natural in speech and writing
• walaupun = very common, slightly more neutral
• meskipun = also common, sometimes feels a bit more formal

So this sentence could also be:

• Walaupun dia bukan teman lama saya...
• Meskipun dia bukan teman lama saya...

Because bukan is used to negate a noun phrase, while tidak is usually used to negate verbs, adjectives, and some other predicates.

Here, teman lama saya is a noun phrase:

• dia bukan teman lama saya = he/she is not my long-time friend

Compare:

• Dia bukan guru. = He/she is not a teacher.
• Dia tidak datang. = He/she did not come.
• Dia tidak senang. = He/she is not happy.

So bukan is correct because the sentence is saying that he/she is not a certain kind of person/friend.

Here, teman lama saya means my long-time friend or a friend I have known for a long time.

It usually does not mean my elderly friend.

In Indonesian, teman lama often refers to the length of the relationship, not the person's age. So the sentence means:

• he/she is not someone I have known for a long time

This is a very common expression:

• teman lama = an old friend / long-time friend
• kenalan lama = an old acquaintance

If you really wanted to emphasize that the friend is old in age, you would usually make that clearer from context or wording.

Yes, Indonesian often allows subjects to be omitted when the meaning is clear, but repeating saya here is completely natural.

The sentence says:

• Biarpun dia bukan teman lama saya, saya mulai mempercayainya...

The second saya helps make the clause clear and balanced:

• first clause: dia is the subject
• second clause: saya is the subject

If you removed it, the sentence might sound less clear:

• Biarpun dia bukan teman lama saya, mulai mempercayainya...
  This feels incomplete or awkward in standard Indonesian.

So repeating saya is normal and helpful.

Mulai mempercayainya means to begin/start trusting him/her.

It breaks down like this:

• mulai = to begin, to start
• mempercayai = to trust
• -nya = him/her (object suffix here)

So:

• saya mulai mempercayainya = I am starting to trust him/her

The verb mempercayai comes from percaya (to believe / to trust) with affixes:

• memper-...-i → mempercayai

This form often means directing trust toward someone or something.

This is a very common question.

Both are related to trust/believe, but they are used a bit differently.

1. percaya

Often means:

• to believe
• to trust

Examples:

• Saya percaya padanya. = I trust him/her.
• Saya percaya itu benar. = I believe that is true.

With people, percaya often appears with pada/kepada:

• percaya pada seseorang = trust someone

2. mempercayai

Usually means:

• to trust someone/something
• to believe in / accept as true

Examples:

• Saya mempercayainya. = I trust him/her.
• Mereka tidak mempercayai cerita itu. = They do not believe that story.

So in this sentence:

• saya mulai mempercayainya means I am starting to trust him/her

A close alternative would be:

• saya mulai percaya padanya

Both are natural, though mempercayainya sounds a bit more direct and compact.

The -nya refers back to dia and means him/her.

So:

• mempercayai = to trust
• mempercayainya = to trust him/her

Important point: Indonesian dia and -nya do not show gender. They can mean:

• him
• her

The exact meaning depends on context.

Because Indonesian often attaches object pronouns as suffixes.

Instead of saying something like trust him/her with a separate object word, Indonesian can say:

• mempercayainya

This is:

• mempercayai
  • -nya

You can think of -nya here as an attached object pronoun.

This is very common in Indonesian:

• melihatnya = see him/her/it
• mendengarnya = hear him/her/it
• membacanya = read it

Karena means because.

It introduces the reason:

• karena dia selalu menepati janji = because he/she always keeps promises

So the logic of the full sentence is:

• Although he/she is not a long-time friend of mine, I am starting to trust him/her because he/she always keeps promises.

Menepati janji means to keep a promise or to fulfill a promise.

Breakdown:

• menepati = to fulfill, observe, keep
• janji = promise

So:

• dia selalu menepati janji = he/she always keeps promises or = he/she always keeps his/her word

This is a very common collocation in Indonesian.

Compare:

• membuat janji = to make a promise / appointment
• menepati janji = to keep a promise
• mengingkari janji = to break a promise

Selalu means always, and in Indonesian it commonly comes before the verb.

So:

• dia selalu menepati janji = he/she always keeps promises

This word order is very normal:

• Saya selalu bangun pagi. = I always wake up early.
• Mereka selalu datang tepat waktu. = They always come on time.

So selalu before the verb is the expected pattern.

It can mean either he or she.

Indonesian third-person singular pronouns usually do not mark gender:

• dia = he / she
• ia = he / she (more formal, often written style)
• -nya = him / her / his / her, depending on context

So you only know the gender if the context tells you.

Yes, that is a very good translation.

A few natural English versions are:

• Even though he/she isn’t a long-time friend of mine, I’m starting to trust him/her because he/she always keeps promises.
• Although he/she is not an old friend of mine, I’m beginning to trust him/her because he/she always keeps his/her word.

The key nuance is that the speaker did not know this person for a long time, but is still beginning to trust them because of their reliable behavior.

Yes. If you want to make the idea of not having known someone for long more explicit, you could say:

• Biarpun saya belum lama mengenalnya...
  = Although I haven’t known him/her for long...

That version is often clearer for learners because it states the idea directly.

But dia bukan teman lama saya is still natural and understandable, especially in context.

The comma is appropriate because the sentence begins with a concessive clause:

• Biarpun dia bukan teman lama saya, ...

This is similar to English:

• Although he isn’t a long-time friend of mine, I’m starting to trust him.

In informal writing, Indonesian punctuation can be looser, but the comma here is good standard punctuation and helps readability.