Learn Hardcore Indonesian: Microwave di rumah rusak, sementara kompor gas masih berfungsi baik. - The microwave at home is broken, while the gas stove still works well.

Microwave di rumah rusak literally is: Microwave at house broken.
Whether it means the microwave at home is broken or a microwave at home is broken is understood from context, not from a separate word.

If you really want to make it specific like that microwave at home, you can add itu:

Microwave di rumah itu rusak.
= That / the microwave at that house is broken.

But in normal conversation, Microwave di rumah rusak is enough to mean the microwave at home is broken if both speakers know which one.

Can I say Microwave rusak di rumah instead of Microwave di rumah rusak?

It is grammatically possible, but it sounds unnatural in normal speech.

Microwave di rumah rusak = The microwave at home is broken.
Here di rumah clearly modifies microwave (which microwave? The one at home).
Microwave rusak di rumah is more likely to be heard as “The microwave broke at the house / at home (as a location of the event).”

So:

To say “the home microwave is broken”, use Microwave di rumah rusak.
To say “the microwave (somewhere) broke while it was at home”, you might use Microwave rusak di rumah, but this is a rarer nuance and context-dependent.

For a learner, it’s safest and most natural to keep di rumah right after the noun it describes: Microwave di rumah rusak.

What is the difference between sementara and sedangkan here? Could I say … rusak, sedangkan kompor gas masih berfungsi baik?

In this sentence, sementara and sedangkan can both be used, and the meaning is almost the same.

sementara here = whereas / while (on the other hand)
Microwave di rumah rusak, sementara kompor gas masih berfungsi baik.
sedangkan = also whereas / while (contrasting two situations)
Microwave di rumah rusak, sedangkan kompor gas masih berfungsi baik.

Nuance:

sementara is slightly more general; it can mean while (at the same time) or whereas.
sedangkan is more focused on showing contrast: A is like this, whereas B is like that.

In everyday use, many native speakers will treat them as interchangeable in contrast sentences like this. Both are fine here.

Does sementara mean “for a while” in this sentence?

No. sementara has a few meanings depending on context:

For a while / temporarily
- Saya tinggal di Jakarta sementara. = I’m staying in Jakarta for a while.
While / whereas / meanwhile (linking two contrasting clauses)
- Dia suka kopi, sementara saya lebih suka teh.
  = He likes coffee, whereas I prefer tea.

In Microwave di rumah rusak, sementara kompor gas masih berfungsi baik, sementara is being used with meaning (2): whereas / while (in contrast), not for a while.

What exactly does rusak mean? Is it like “broken” as in physically broken into pieces?

rusak is broader than English broken.

It means damaged / not working / spoiled, and it does not necessarily mean something is in pieces.

Examples:

Microwave di rumah rusak.
The microwave is not functioning properly / broken (mechanically or electronically).
Mobilnya rusak.
The car is broken down / not working.

Compare with more specific words:

pecah = shattered / broken into pieces (glass, plate, etc.)
Gelasnya pecah. = The glass is shattered/broken (into pieces).
patah = broken in two / snapped (bones, sticks, poles).
Kakinya patah. = His leg is broken (bone fracture).

So for appliances or machines that don’t work, rusak is the standard word.

What does masih add to kompor gas masih berfungsi baik?

masih means still.

kompor gas berfungsi baik = the gas stove functions well.
kompor gas masih berfungsi baik = the gas stove still functions well.

In this sentence, masih emphasizes that even though the microwave is broken, the gas stove is still okay.

Without masih, you lose that “in contrast to the first clause” feel, although the sentence is still grammatically correct.

Is berfungsi baik correct, or should it be berfungsi dengan baik?

Both are used, but there is a nuance:

berfungsi baik = functions well
This is understandable and natural in casual speech.
berfungsi dengan baik = functions well / functions properly
This is a bit more complete and often sounds slightly more formal or careful.

Grammatically, baik is an adjective. When used as an adverb (“well”), you often see dengan:

berjalan dengan baik = go/run/function well
bekerja dengan baik = work well

So in writing (especially formal writing), berfungsi dengan baik is the “textbook-perfect” form.
In daily conversation, berfungsi baik is also heard and accepted.

Why is it kompor gas, not just kompor? What does kompor gas literally mean?

kompor = stove / cooker, in general.
kompor gas = gas stove (a stove that uses gas).

You can specify types:

kompor gas = gas stove
kompor listrik = electric stove
kompor minyak = kerosene stove

In everyday speech, people often say kompor if it’s obvious what type they mean.
In this sentence, kompor gas just clarifies the kind of stove that still works.

Is microwave commonly used as a loanword like that in Indonesian, or is there a more “Indonesian” word?

Indonesian commonly uses the loanword microwave (often written microwave or sometimes oven microwave).

You may see:

microwave
oven microwave
oven (in some contexts, though that can also mean a conventional oven)

There is no widely used pure-Indonesian alternative that replaces microwave in everyday speech. So sentences like:

Microwave di rumah rusak.
are completely natural.

Also, as a common noun, it is usually not capitalized in standard writing: microwave, not Microwave, unless it’s at the start of the sentence.

How do I say “my microwave at home is broken”? Where do I put my in Indonesian?

You can add a possessive after rumah or after microwave, depending on what you want to emphasize.

Natural options:

Microwave di rumah saya rusak.
Literally: Microwave at my house is broken.
Very natural and common.
Microwave saya di rumah rusak.
Literally: My microwave at home is broken.
Also correct; emphasizes microwave saya (my microwave).
More informal:
- Microwave di rumahku rusak.
- Microwave aku di rumah rusak. (less common; microwave aku sounds casual/colloquial)

In everyday speech, Microwave di rumah saya rusak is probably the safest and most neutral.

How do we know if this sentence is talking about the present or the past? There is no tense marker.

Indonesian verbs do not change form for tense (no -ed, no -s, etc.).
Time is understood from context or from time words.

Microwave di rumah rusak, sementara kompor gas masih berfungsi baik.

By itself, this can mean:

The microwave at home is broken, whereas the gas stove still works. (present)
or
The microwave at home was broken, whereas the gas stove still worked. (past)

To be explicit:

Tadi pagi, microwave di rumah rusak…
This morning, the microwave at home broke…
Sekarang, microwave di rumah rusak…
Now, the microwave at home is broken…

Without such markers, Indonesian leaves it to context.

Does di rumah always mean “at home”? Could it also mean “in the house”?

di rumah can mean both at home and in the house, depending on context.

Saya di rumah.
= I am at home.
Ada tikus di rumah.
= There is a mouse in the house / at home.

In Microwave di rumah rusak, it is most naturally understood as:

The microwave at home is broken.

You could also interpret it literally as “the microwave in the house is broken”, but in everyday speech di rumah is strongly associated with “at home”.

Why is there a comma before sementara? Is that required?

The comma before sementara is standard and helpful, but not absolutely “required” in all casual writing.

You have two clauses:

Microwave di rumah rusak
sementara kompor gas masih berfungsi baik

Linking them with sementara as a conjunction, you typically separate the clauses with a comma:

Microwave di rumah rusak, sementara kompor gas masih berfungsi baik.

This mirrors English usage with whereas or while:

The microwave at home is broken, whereas the gas stove still works.

In informal texting or chat, many Indonesians may drop the comma, but in proper writing, the comma is recommended.