Sebelum ujian, saya mematikan notifikasi di gawai supaya bisa fokus.

It’s optional but common. Sebelum ujian is an introductory time phrase (Before the exam), and Indonesian often uses a comma after such fronted phrases to make the sentence easier to read. You can also write it without the comma:

• Sebelum ujian saya mematikan notifikasi di gawai supaya bisa fokus.

It generally means before the exam (in general), which usually implies before it starts, but it’s not as explicit as English sometimes is. If you want to be clearer, you can say:

• Sebelum ujian dimulai, ... = Before the exam starts, ...

Yes. Sebelum can be followed by:

• a noun phrase: sebelum ujian = before the exam
• a verb/clause: sebelum ujian dimulai = before the exam begins, sebelum pergi = before leaving

Mematikan means to turn off / to switch off / to disable (something). It comes from the root mati (dead/off) and the verb-forming prefix meN- plus -kan, making it a transitive verb:

• mati = be off / be dead (state)
• mematikan (sesuatu) = to make something off (action), i.e. turn something off

It’s natural and understandable. Common alternatives include:

• menonaktifkan notifikasi = disable notifications (more “settings/technical”)
• mematikan notifikasi = turn off notifications (more general) Both are used; menonaktifkan can sound slightly more “system/settings” specific.

Indonesian usually doesn’t mark plural the same way English does. Notifikasi can mean notification or notifications depending on context. If you really want to emphasize plural, you can say:

• notifikasi-notifikasi (reduplication) = notifications (emphatic/explicit) But it’s often unnecessary.

Functionally it means on the device / on my device (i.e., on the phone/tablet). Indonesian uses di for location broadly, and with digital things it often maps to English on:

• notifikasi di gawai = notifications on the device

Gawai is correct and used in Indonesian, but it can sound a bit formal/standardized (often seen in writing, news, UI language). In everyday speech, many people say:

• HP (very common) = phone
• ponsel = mobile phone
• telepon = phone (general) So you could also say: di HP or di ponsel.

Both mean so that / in order that and are often interchangeable.

• supaya is very common in everyday speech.
• agar can sound slightly more formal/written (though still normal in speech). In this sentence, either works:
• ... supaya bisa fokus.
• ... agar bisa fokus.

Indonesian often drops the subject when it’s obvious from context. Since the subject is already saya in the main clause, it’s understood in the purpose clause too:

• supaya (saya) bisa fokus = so that (I) can focus

It works like a predicate/adjective meaning focused. With bisa, the phrase bisa fokus is like can be focused / can focus. Indonesian is flexible about word classes; fokus can act like:

• adjective: Saya fokus. = I’m focused.
• verb-like predicate: Saya fokus belajar. = I focus on studying.