Anak saya berhenti berlari ketika melihat bintang jatuh di pantai.

Berhenti berlari literally means “stop running.” In Indonesian, when you use berhenti (to stop) followed by another verb, you don’t insert untuk. If you added untuk, as in berhenti untuk berlari, it would shift the meaning to “stop in order to run,” which is not what we want here. The structure is simply:

• berhenti
  • bare verb = stop [doing something].

The prefix ber- is very common in Indonesian to create intransitive verbs—verbs that don’t take an object.

• henti (root) means “stop,” but it’s usually seen in compounds or with a prefix/suffix.
• ber-
  • henti = berhenti, “to stop.”
    You’ll see ber- on other intransitive verbs:
• berjalan (walk) from jalan,
• bekerja (work) from kerja.

Indonesian often drops the subject in subordinate clauses when it’s the same as the main clause’s subject. Here:

• Main clause subject: Anak saya (“My child”)
• Subordinate clause subject: implied to be the same, so you just say melihat… without repeating anak saya.

If a different person were doing the seeing, you would state it: ketika dia melihat… (“when he/she saw…”).

ketika is a conjunction that means “when” in temporal clauses.

• ketika and saat are largely interchangeable: ketika hujan turun ≈ saat hujan turun (“when it rains”).
• waktu is primarily a noun meaning “time,” but you can make it function like a conjunction by adding “saat” or “ketika”:
  
  • waktu saya kecil, saya suka… (“when I was small, I liked…”).
    Note: ketika/​saat are a bit more formal than waktu in this usage.

In Indonesian, di marks a static location (“at,” “in,” “on”), whereas ke marks direction or destination (“to”).

• melihat bintang jatuh di pantai = “saw a falling star on/at the beach.”
• If you wanted to say “go to the beach,” you’d use ke pantai: saya pergi ke pantai.

The standard Indonesian order for possession is [head noun] + [possessor].

• Anak saya = “my child” (literally “child mine”).
  If you reversed it to saya anak, it would sound like a simple noun phrase meaning “I child” or be ungrammatical. You could use affixes like -ku (anakku) for colloquial “my child,” but the head-noun-then-possessor order stays the same.

bintang jatuh literally means “falling star.” It refers to the same phenomenon we call a shooting star in English—a meteor burning up in the atmosphere.

• bintang = star
• jatuh = fall/falling
  In everyday speech, Indonesians use bintang jatuh for that brief streak of light.

Sure. Anak saya berhenti berlari ketika melihat bintang jatuh di pantai

• Anak = child
• saya = my (lit. “I”)
• berhenti = stopped
• berlari = running
• ketika = when
• melihat = saw/seeing
• bintang = star
• jatuh = falling
• di = at/on/in
• pantai = beach

Putting it all together: “My child stopped running when (he/she) saw a shooting star on the beach.”