Learn Hardcore Indonesian: Kami berkoordinasi lewat pesan, lalu bertemu tatap muka siang ini. - We coordinate via messages, then meet face-to-face this afternoon.

So kami is correct if the speaker is telling someone who was not part of the coordination/meeting. If the listener was involved, you’d use kita instead.

What does the prefix ber- in berkoordinasi tell me?

The prefix ber- often makes an intransitive verb describing an action the subject performs or engages in (often mutual or without a direct object). Berkoordinasi means “to coordinate (with each other/with others).” It doesn’t take a direct object.

If you want a transitive form (coordinate something), use:

mengoordinasikan or mengkoordinasikan
- object (both are widely used; style guides often prefer mengoordinasikan). Example: Dia mengoordinasikan rapat.

Is lewat the same as melalui or via?

All can mean “through/by (means of)”:

lewat: everyday, casual. Example: lewat pesan.
melalui: more formal/neutral. Example: melalui pesan.
via: borrowed, common in writing or casual speech. Example: via WhatsApp.

What exactly does pesan refer to here?

Pesan is generic “message.” It could be text message, WhatsApp, Telegram, email, or in-app chat. If you want to be specific:

pesan teks (text message/SMS)
pesan WhatsApp/WA
chat (casual)

What nuance does lalu have compared with kemudian and terus?

All roughly mean “then/after that”:

lalu: neutral and common in narratives.
kemudian: a bit more formal or written.
terus: very casual, conversational.
Your sentence could be: …, kemudian bertemu … (more formal) or …, terus ketemu … (casual).

Why isn’t kami repeated before bertemu?

Indonesian often drops a repeated subject in the next clause if it’s the same. So Kami …, lalu bertemu … is natural. You can repeat it for emphasis or clarity (…, lalu kami bertemu …), but it’s not required.

Is bertemu tatap muka redundant? Could I just say bertatap muka?

Both are fine:

bertemu tatap muka = “meet face-to-face” (very common and clear).
bertatap muka is also natural and slightly more compact, often used in formal writing.
You can also say bertemu langsung or bertemu secara langsung (“meet in person/directly”).

Do I need dengan after bertemu?

Not necessarily. You can say:

bertemu [person] or bertemu dengan [person] (both are common). But don’t say bertemu dengan tatap muka—use bertemu tatap muka or bertemu secara tatap muka (the latter is more formal but a bit wordy).

What’s the difference between bertemu, menemui, and ketemu?

bertemu: neutral/standard “to meet,” can be intransitive or take a person as complement. Example: Saya bertemu dia.
menemui: transitive “to go to meet/visit (someone)”—focus on seeking someone out. Example: Saya menemui atasan saya.
ketemu: casual/colloquial for “meet/run into” or “find.” Example: Kita ketemu nanti siang.

Does siang ini mean past or future?

Indonesian has no tense marking. Siang ini = “this afternoon (today).”

If said in the morning, it implies a future time today.
If said in the evening, it refers to earlier today.
You can be explicit:
nanti siang (later this afternoon)
tadi siang (earlier this afternoon)

Should I add a preposition before siang ini, like pada or di?

Bare siang ini is the most natural.
pada siang ini is more formal or emphatic (often in official writing).
di siang ini is generally avoided. You’ll see di siang hari for a general statement about daytime, not a specific “this afternoon.”

Is pesan singular or plural here?

Indonesian doesn’t mark plural by default. lewat pesan can mean “through message(s).” If you must emphasize plurality, you can say pesan-pesan, though it’s rarely needed here because the medium (messaging) is what matters.

Can I move siang ini to another position?

Yes. Word order is flexible for adverbials:

Neutral: …, lalu bertemu tatap muka siang ini.
Time-first (emphasis on when): Siang ini kami berkoordinasi lewat pesan, lalu bertemu tatap muka.
Between verb and complement (less common, but possible): …, lalu siang ini bertemu tatap muka.

Is the comma before lalu required?

It’s conventional (and helpful) to put a comma before lalu when it separates two clauses or actions. Many editors allow either style, but the comma improves readability.

How do I pronounce the tricky parts?

Approximate syllables:

ber-ko-or-di-na-si
le-wat
pe-san
la-lu
ber-te-mu
ta-tap mu-ka
si-ang i-ni
Stress is light and fairly even; don’t over-stress syllables as in English.

How would this look in a more casual or more formal register?

Casual: Kami koordinasi lewat chat, terus ketemu langsung nanti siang.
Formal: Kami berkoordinasi melalui pesan, kemudian bertatap muka pada siang hari ini.
Adjust kami/kita depending on whether you include the listener.