Learn Hardcore Indonesian: Saat kabut turun, dia memakai sepatu bot dan berjalan pelan. - When fog comes down, he/she wears boots and walks slowly.

Ketika kabut turun – almost the same meaning; ketika is very common in written and spoken Indonesian.
Waktu kabut turun – also possible, slightly more informal / conversational.

In most everyday contexts:

saat / ketika / waktu are interchangeable when they introduce a time clause like this.
saat and ketika feel a bit more neutral/formal than waktu.

So:

Saat kabut turun, ...
Ketika kabut turun, ...
Waktu kabut turun, ...

all work here with essentially the same meaning.

Is kabut turun literally fog goes down? Is this a natural phrase in Indonesian?

Yes. Literally:

kabut = fog
turun = to go down / to descend / to fall

So kabut turun literally looks like the fog goes down / comes down.

This is a natural, common way in Indonesian to say the fog comes in / the fog descends.

Other natural variants:

ketika kabut mulai turun – when the fog starts to come down
saat kabut tebal turun – when thick fog comes down

You would not normally say kabut datang in this context; kabut turun is the standard collocation.

Why is it Saat kabut turun and not Saat turun kabut? Can the order be reversed?

The normal order for this kind of clause is:

Subject + Verb → kabut turun (fog descends)

So:

Saat kabut turun is the standard form.

If you say Saat turun kabut, it sounds odd or poetic, not normal conversational Indonesian. You might sometimes see inverted orders in poetry, song lyrics, or very stylized language, but for everyday speech and writing, keep:

kabut turun, not turun kabut.

Does dia mean he or she? How do Indonesians show gender?

Dia is gender-neutral. It can mean:

he
she

Indonesian pronouns generally do not show gender. Native speakers know whether dia refers to a man or a woman from context, not from the word itself.

If you want to make gender explicit, you can:

Use a noun instead of a pronoun:
- laki-laki itu / pria itu = that man
- perempuan itu / wanita itu = that woman

But normally, dia is enough, and people understand from context.

What is the difference between memakai and pakai? Could we say dia pakai sepatu bot?

Memakai and pakai both mean to wear or to use.

memakai – more complete, slightly more formal or neutral.
pakai – shorter, more informal/colloquial.

In this sentence:

dia memakai sepatu bot – correct, neutral.
dia pakai sepatu bot – also correct, sounds more casual.

In everyday spoken Indonesian, dia pakai sepatu bot is extremely common. In more formal writing, memakai (or mengenakan) is preferred:

dia mengenakan sepatu bot – more formal/literary.

What exactly does sepatu bot mean? Is it singular or plural?

Sepatu bot literally is:

sepatu = shoe (but usually used for shoes in general)
bot (from English boot) = boot

Together, sepatu bot means boots (as a type of footwear).

Indonesian normally does not mark singular vs plural on the noun itself, so:

sepatu bot can mean a boot, a pair of boots, or boots in general.
Context usually makes it clear. Here, it naturally means a pair of boots.

If you really need to emphasize the quantity, you can add a classifier:

sepasang sepatu bot = one pair of boots
dua pasang sepatu bot = two pairs of boots

You would not usually say just bot by itself for footwear; sepatu bot is the standard phrase.

Why is it dia memakai sepatu bot dan berjalan pelan, without repeating dia? Should it be dia memakai ... dan dia berjalan ...?

In Indonesian, when two verbs share the same subject, you often:

mention the subject once
then list the verbs with dan (and) after it

So:

dia memakai sepatu bot dan berjalan pelan
literally: he/she wore boots and walked slowly

Here, dia is the subject of both memakai and berjalan. Repeating dia is not wrong, but it sounds heavier and less natural:

dia memakai sepatu bot dan dia berjalan pelan – grammatically okay, but a bit clunky in normal speech.

So the given sentence is the more natural structure.

Why is there a comma after Saat kabut turun? Is the word order flexible?

The sentence is:

Saat kabut turun, dia memakai sepatu bot dan berjalan pelan.

This has two parts:

A time clause: Saat kabut turun
The main clause: dia memakai sepatu bot dan berjalan pelan

When a time clause like saat kabut turun comes at the beginning, Indonesian normally uses a comma between the clauses.

You can also reverse the order:

Dia memakai sepatu bot dan berjalan pelan saat kabut turun.

Both are correct. Differences:

Saat kabut turun, ... – focuses first on the condition/time.
Dia memakai sepatu bot ... saat kabut turun. – starts with what dia does.

The meaning is the same; the word order is flexible here.

How do we know this is past tense? There is no word like did or was.

Indonesian verbs do not change form for tense (past, present, future). There is no equivalent of English verb endings or did / was / will built into the verb.

memakai can mean wears / is wearing / wore
berjalan can mean walks / is walking / walked

The time is usually understood from:

context (previous sentences, the situation)
time words, if added:
- tadi = earlier / just now
- kemarin = yesterday
- besok = tomorrow
- akan = will / going to

If you really want to make it clear it happened in the past, you can say, for example:

Tadi saat kabut turun, dia memakai sepatu bot dan berjalan pelan.
Earlier, when the fog came down, he/she wore boots and walked slowly.

But the original sentence can describe a past event if the context is past.

What is the nuance of pelan? How is it different from pelan-pelan or perlahan?

All of these relate to slowly:

pelan – slow; adverbially slowly. Neutral, everyday word.
pelan-pelan – literally slow-slow; more informal, often sounds softer or more emphatic (like slowly, okay?).
perlahan / perlahan-lahan – more formal/neutral; often preferred in writing.

In this sentence:

berjalan pelan = walked slowly (neutral)
berjalan pelan-pelan = walked very slowly / walked slowly, gently (more informal, a bit more expressive)
berjalan perlahan / berjalan perlahan-lahan = walked slowly (slightly more formal or descriptive in writing)

All are understandable; the original pelan is a natural, neutral choice.

Could we say berjalan dengan pelan instead of berjalan pelan?

Yes, you can say:

berjalan dengan pelan = walked slowly

But in everyday Indonesian, berjalan pelan (adjective directly after the verb) is more common and simpler.

Patterns:

Very common: berjalan pelan, berbicara pelan, bergerak cepat
Also acceptable but less common in casual speech: berjalan dengan pelan, berbicara dengan pelan

In more formal writing, dengan + adjective/adverb is slightly more common, but not required.

Why is it berjalan pelan and not just jalan pelan? Is jalan also a verb?

Both are possible:

berjalan pelan – more standard/neutral.
jalan pelan – common in informal speech.

Jalan can be:

a noun = road / street / way
a verb = to walk

The prefix ber- in berjalan makes it clearly verbal (to walk), and is more standard Indonesian.

In everyday conversation, people often drop ber- and simply say:

Dia jalan pelan. – He/She walks slowly.

In writing or in more careful speech, berjalan pelan is preferred.

Could we replace dan with lalu here? What’s the difference?

Current sentence:

dia memakai sepatu bot dan berjalan pelan
= he/she wore boots and walked slowly

If you say:

dia memakai sepatu bot lalu berjalan pelan

then:

dan = and (just links two actions; they can be simultaneous or sequential depending on context).
lalu = then / and then (more clearly shows sequence: first memakai, then berjalan).

So lalu puts more emphasis on the order of actions:

put on boots
then started walking slowly

Both are correct; dan is more neutral; lalu explicitly marks then.