Learn Hardcore Indonesian: Pelatih olahraga kami melatih tim futsal setiap Sabtu malam. - Our sports coach trains the futsal team every Saturday night.

If you say kami pelatih olahraga, it means we are sports coaches, not our sports coach.
So the correct order for possession is noun + pronoun, not pronoun + noun.

Does pelatih olahraga kami mean “our sports coach” or “our sports coaches”?

On its own, pelatih olahraga kami is not marked for singular or plural. It can mean:

our sports coach (one)
our sports coaches (more than one)

Context usually makes it clear.
If you really need to show it’s plural, you can say:

para pelatih olahraga kami (our sports coaches – more formal)
pelatih-pelatih olahraga kami (our coaches – with repetition to show plural)

Why is it tim futsal and not futsal tim?

In Indonesian, the typical order is:

main noun + describing word / type

So:

tim futsal = futsal team
tim basket = basketball team
buku matematika = math book
guru bahasa Inggris = English teacher

Putting it as futsal tim would sound wrong to Indonesian ears.
Tim is the core noun, and futsal tells you what kind of team it is.

How would I say “our futsal team” in this sentence?

You add kami after tim futsal, just like with other possessives:

tim futsal kami = our futsal team

So a version that says our sports coach trains our futsal team every Saturday night would be:

Pelatih olahraga kami melatih tim futsal kami setiap Sabtu malam.

Why is it setiap Sabtu malam and not pada Sabtu malam?

Setiap means every, so setiap Sabtu malam = every Saturday night.

The preposition pada (at/on) is optional with times and dates:

(Pada) Sabtu malam = on Saturday night
(Pada) pukul tujuh = at seven o’clock

With setiap, Indonesians normally just say:

setiap Sabtu malam
rather than
pada setiap Sabtu malam

You can say pada setiap Sabtu malam, but it sounds more formal and heavier in everyday speech.

Is there a difference between Sabtu malam and malam Sabtu?

Yes, and it can be confusing.

Sabtu malam normally means Saturday night (the night after Saturday daytime).
malam Sabtu is usually understood as Friday night, i.e. the night before Saturday (literally “the night heading into Saturday”).

Similarly:

Minggu malam = Sunday night
malam Minggu = Saturday night

In your sentence, setiap Sabtu malam is every Saturday night.
If you said setiap malam Sabtu, many Indonesians would understand every Friday night.

Can setiap Sabtu malam go at the beginning of the sentence?

Yes. Time expressions are quite flexible in Indonesian. All of these are grammatical:

Pelatih olahraga kami melatih tim futsal setiap Sabtu malam.
Setiap Sabtu malam, pelatih olahraga kami melatih tim futsal.
Pelatih olahraga kami setiap Sabtu malam melatih tim futsal. (possible but less natural)

The most natural are usually:

[subject] [verb] [object] [time]
or [time], [subject] [verb] [object]

Do days of the week like Sabtu always start with a capital letter?

Yes. According to standard Indonesian spelling:

Days of the week are capitalized: Senin, Selasa, Rabu, Kamis, Jumat, Sabtu, Minggu
Months are also capitalized: Januari, Februari, etc.
Words like malam, pagi, tim, futsal are not capitalized unless they start a sentence or are part of a proper name.

So Sabtu malam is written with Sabtu capitalized and malam in lower case.

How can I change this sentence to past or future tense?

Indonesian doesn’t change the verb form. You add time words instead.

For a past, habitual meaning (used to train every Saturday night), you can say:

Dulu pelatih olahraga kami melatih tim futsal setiap Sabtu malam.
(In the past, our sports coach trained the futsal team every Saturday night.)

For a future meaning (will train every Saturday night), add akan or a future time expression:

Mulai bulan depan, pelatih olahraga kami akan melatih tim futsal setiap Sabtu malam.
(Starting next month, our sports coach will train the futsal team every Saturday night.)

The verb melatih itself does not change; the time words carry the tense/aspect information.

Can I drop olahraga and just say pelatih kami?

Yes, grammatically you can:

Pelatih kami melatih tim futsal setiap Sabtu malam.

This then means our coach (not specifically “sports coach”).
Whether that’s natural depends on context:

If everyone already knows you’re talking about a sports context, pelatih kami is fine.
If you want to be clear it’s a sports coach (not, for example, a vocal coach or a debate coach), then pelatih olahraga kami is better.

Can I omit kami altogether?

Yes, but the meaning changes.
If you say:

Pelatih olahraga melatih tim futsal setiap Sabtu malam.

it means (The) sports coach trains the futsal team every Saturday night, with no “our”.
It sounds like a general statement about some coach, not specifically someone belonging to “us”.

In real conversations, Indonesians sometimes drop kami/kita if it’s already very clear from context, but grammatically kami is what makes it “our”.

Is tim always used for sports teams, and is it a loanword?

Yes, tim is a loanword from English team, and it is widely used for sports and other organized groups:

tim futsal = futsal team
tim nasional = national team
tim peneliti = research team

There is another word, kesebelasan, but that is specific to an 11‑player football (soccer) team. Because futsal has 5 players, kesebelasan futsal would sound wrong; tim futsal is the natural phrase.

Could I say melatihkan instead of melatih here?

In this sentence, melatih is the correct and natural choice.

melatih = to train someone / a team
- Pelatih olahraga kami melatih tim futsal.
melatihkan usually has a different pattern, often meaning to train (something) for someone or to have someone trained, and it’s much less common. It doesn’t fit well with tim futsal as a direct object.

So you should stick with:

Pelatih olahraga kami melatih tim futsal setiap Sabtu malam.