Mereka bergaduh semalam.

Malay verbs normally do not change for tense, person, or number.

So bergaduh stays bergaduh with:

• saya
• dia
• kami
• mereka

The past meaning comes from semalam, which gives the time reference. That is why no extra verb ending is needed.

You can add words like sudah or telah in some contexts, but in this sentence they are unnecessary.

Ber- is a very common Malay prefix. With many roots, it forms an intransitive verb meaning something like to do, to be engaged in, or sometimes to do together / mutually.

Here:

• gaduh = the root
• bergaduh = to quarrel / argue / fight

In this sentence, bergaduh is the normal standard verb form.

In casual spoken Malay, many speakers do say gaduh without ber-.

So:

• Mereka bergaduh semalam = more standard / careful
• Mereka gaduh semalam = common in informal speech

If you are learning standard Malay, bergaduh is the safer form to use.

It can cover both, depending on context.

It often means:

• to quarrel
• to argue
• to fight

If you want to be more specific:

• bertengkar usually points more clearly to a verbal argument
• berkelahi usually points more clearly to a physical fight

So bergaduh is a broad, everyday word.

In standard Malay, semalam commonly means yesterday.

Depending on context, English translations sometimes make it sound closer to last night, but if you want to say last night very clearly, malam tadi is often a clearer choice.

So for learners, the safest basic idea is:

• semalam = yesterday
• malam tadi = last night

Yes, it can go at the beginning.

Both are natural:

• Mereka bergaduh semalam.
• Semalam mereka bergaduh.

The version with semalam at the end sounds neutral and very common. Putting semalam first gives a little more focus to the time.

Because mereka already includes both sides, and bergaduh already suggests a mutual action.

So Mereka bergaduh already naturally means they argued/fought with each other.

You would use dengan if the other person or group is mentioned separately, for example:

• Ali bergaduh dengan adiknya.

But when both parties are already included in mereka, no extra with word is needed.

Normally, no.

In Malay, mereka is a plural pronoun, usually for people. It does not normally work like singular English they.

So:

• mereka = plural they
• dia = he / she
• beliau = a more respectful he / she

Also, mereka is mainly used for humans. For animals or things, Malay often repeats the noun instead of using mereka, unless the speaker is personifying them.