Mereka menjual semua harta mereka.

Because the two instances do different jobs:

• the first mereka = the subject: they
• the second mereka = the possessor: their

Malay often uses the same pronoun form in different roles. Possession is usually shown with:

noun + pronoun

So:

• harta mereka = their property/assets
• rumah mereka = their house
• kereta mereka = their car

Unlike English, Malay does not change they into their.

Menjual is the standard active verb form built from the root jual (sell).

• root: jual
• verb form: menjual

The prefix meN- makes it a normal active verb in standard Malay, especially in writing and careful speech.

So menjual is the expected standard form in a sentence like this.

You may hear jual by itself in casual speech, but menjual is better for formal/standard Malay.

It can mean any of those, depending on context.

Malay verbs usually do not change form for tense the way English verbs do. So menjual does not itself mark past, present, or future.

The time is usually understood from context or from time words such as:

• semalam = yesterday
• sekarang = now
• esok = tomorrow

So this sentence could be understood as:

• they sell all their property
• they are selling all their property
• they sold all their property

Context tells you which one is meant.

Because semua normally comes before the noun it quantifies.

So:

• semua harta mereka = all their property/assets

This is the normal pattern:

• semua orang = all people
• semua buku = all the books
• semua harta = all the property/assets

Compare that with mereka semua, which means all of them. That is a different structure.

Malay nouns usually do not have a special form for singular versus plural.

So harta by itself does not have to be marked as singular or plural the way English nouns often are. In this sentence, semua already makes it clear that the meaning is all of their property/assets.

Also, harta often works like a collective or mass noun in English, similar to property, wealth, or assets.

Harta usually means something like:

• property
• wealth
• assets
• possessions of value

It sounds broader and often more serious than just stuff or things.

So this sentence suggests they sold off everything of value they owned, not just random objects.

If you wanted to talk more about ordinary physical things, words like barang or benda might be more natural in some contexts.

You can, but the meaning changes.

• Mereka menjual semua harta mereka = they sold all their property
• Mereka menjual semua harta = they sold all the property / all property

Without the second mereka, the sentence no longer explicitly says that the property belonged to them.

If ownership matters, keep mereka.

No. Mereka is gender-neutral.

It can refer to:

• all men
• all women
• a mixed group

Malay does not normally distinguish they by gender.

Also, mereka is generally used for people, not usually for objects.

Yes, in informal spoken Malay, that is very common.

In everyday speech, speakers often drop prefixes like meN-, so:

• Mereka jual semua harta mereka sounds casual and conversational.
• Mereka menjual semua harta mereka sounds standard and is better for formal writing, teaching materials, news style, and careful speech.

So both can occur, but menjual is the safer choice for learners when aiming for standard Malay.