Saya tidak bisa tidur karena gigi saya sakit.

The first saya is the subject: I.

The second saya shows possession: my tooth/teeth.

So the sentence is structured like this:

• Saya = I
• gigi saya = my tooth / my teeth

Indonesian often uses the same word for I and my, depending on position and function in the sentence.

In Indonesian, possessors usually come after the noun.

So:

• gigi saya = my tooth / my teeth
• rumah saya = my house
• nama saya = my name

This is normal Indonesian word order. English says my tooth, but Indonesian says tooth my.

It can mean either one.

Indonesian nouns usually do not change form for singular vs. plural. So gigi can mean:

• tooth
• teeth

Context tells you which meaning is intended. In this sentence, English might naturally translate it as either:

• my tooth hurts
• my teeth hurt

If you really need to make it clearly plural, Indonesian can use reduplication:

• gigi-gigi saya = my teeth

But in normal speech, that is often unnecessary.

Because tidak negates verbs and adjectives, and here it is negating bisa.

• bisa tidur = can sleep / be able to sleep
• tidak bisa tidur = cannot sleep / not able to sleep

So tidak comes before the word it negates.

Compare:

• Saya bisa tidur = I can sleep
• Saya tidak bisa tidur = I cannot sleep

Here, bisa means can or be able to.

So:

• bisa tidur = can sleep / be able to sleep

In this sentence, Saya tidak bisa tidur is a very natural way to say I can’t sleep.

A small extra note: bisa can also mean poison in other contexts, but that is a completely different meaning. In this sentence, it clearly means can / be able to.

Karena means because.

It introduces the reason:

• Saya tidak bisa tidur = I can’t sleep
• karena gigi saya sakit = because my tooth/teeth hurt

So the whole sentence means:

• I can’t sleep because my tooth hurts or
• I can’t sleep because my teeth hurt

Yes. Indonesian allows that.

You can say:

• Saya tidak bisa tidur karena gigi saya sakit.
• Karena gigi saya sakit, saya tidak bisa tidur.

Both are correct. The second version puts more emphasis on the reason first.

Here, sakit means hurt / painful.

That is because it is describing a body part:

• gigi saya sakit = my tooth hurts / my teeth hurt

With people, sakit can also mean sick / ill:

• Saya sakit = I am sick

So the meaning depends on what sakit is describing.

Because Indonesian does not normally use articles like English a, an, or the.

So Indonesian often says simply:

• gigi saya sakit

instead of something like the my tooth hurts or a tooth of mine hurts.

English requires articles in many places, but Indonesian usually does not.

Yes, you could.

• saya is more neutral or polite
• aku is more casual and personal

Also, instead of gigi saya, you can attach the possessive suffix -ku:

• gigiku = my tooth / my teeth

So:

• Saya tidak bisa tidur karena gigi saya sakit.
  is polite/neutral.

• Aku tidak bisa tidur karena gigiku sakit.
  is more casual and very natural in everyday speech.

Both are correct.

Yes, but tidak bisa tidur is usually more common and natural in everyday conversation.

Both can mean can’t sleep:

• tidak bisa tidur = can’t sleep
• tidak dapat tidur = can’t sleep

In many contexts, dapat sounds a bit more formal than bisa.

Because gigi saya sakit is the natural way to say that a tooth hurts.

• sakit describes the condition: painful / hurting
• menyakitkan usually means painful in the sense of causing pain, and it is less natural for a simple statement about a body part hurting

So learners should remember:

• Kepala saya sakit = My head hurts
• Perut saya sakit = My stomach hurts
• Gigi saya sakit = My tooth hurts

That pattern is very common in Indonesian.

You could in some contexts, but it would usually sound less specific.

• gigi saya sakit = my tooth hurts / my teeth hurt
• gigi sakit = a tooth hurts / teeth hurt / toothache-related, but without clearly saying whose

If you are talking about your own tooth, keeping saya makes the sentence clearer and more natural.