Learn Hardcore Malay: Kami membawa salad buah ketika berkelah di tasik. - We bring fruit salad when picnicking at the lake.

In Kami membawa salad buah ketika berkelah di tasik, the speaker is talking about their group only, not including the listener. That’s why kami is used.

If you wanted to include the listener (e.g. “We (you and I) brought fruit salad…”), you would use kita instead:
Kita membawa salad buah…

How do I know this is past tense (“brought”) when membawa does not change form?

Malay verbs usually do not change form for tense. Membawa can mean:

bring / is bringing / will bring / brought

The tense is understood from context or with time words, for example:

Semalam kami membawa salad buah.
Yesterday we brought fruit salad.
Esok kami akan membawa salad buah.
Tomorrow we will bring fruit salad.

In the sentence you gave, English naturally prefers “brought”, but Malay itself doesn’t mark the past tense explicitly.

What does membawa literally mean, and how is it formed?

The base verb is bawa = to carry / to bring.
With the prefix meN-, it becomes membawa.

bawa – more informal / casual speech
membawa – more neutral / standard / formal

Both are common. In everyday conversation, you’ll often hear:

Kami bawa salad buah…

In writing or more formal speech, membawa sounds slightly more proper.

Why is it salad buah instead of buah salad?

Malay usually follows this general order:

main noun + describing noun
(head noun) (what kind / of what)

So:

salad buah = fruit salad (salad of fruit)
jus oren = orange juice (juice of orange)
kuih beras = rice cake (cake of rice)

If you said buah salad, it would literally be “fruit of salad”, which sounds wrong or at least very odd. So the natural order is salad buah.

Is there any difference between salad buah and salad buah-buahan?

Both are understandable and used:

salad buah – fruit salad (simple, very common)
salad buah-buahan – fruit salad, with buah-buahan meaning “fruits (various kinds of fruit)”

Buah-buahan is the plural/collective form of buah. Using salad buah-buahan can subtly emphasize that there are many kinds of fruit in the salad, but in practice people often just say salad buah.

What does ketika mean, and how is it different from words like semasa, apabila, or bila?

Ketika means when / while (at the time that…). In most everyday contexts, it’s similar to:

semasa – while / when
apabila – when (more formal / written)
bila – when (very common in speech, more informal)

In your sentence:

Kami membawa salad buah ketika berkelah di tasik.
We brought fruit salad when we were having a picnic at the lake.

You could replace ketika with semasa or apabila without changing the meaning much:

…semasa berkelah di tasik.
…apabila berkelah di tasik.

Bila is more casual: …bila kami berkelah di tasik.

What does berkelah mean, and what is the role of the ber- prefix?

The base word is kelah, and with ber- it becomes berkelah.

berkelah = to have a picnic / to go on a picnic

The prefix ber- often forms intransitive verbs (no direct object), often meaning “to do / be engaged in / have [X]”:

berjalan – to walk
berlari – to run
bercakap – to talk
berkelah – to have a picnic

So ketika berkelah di tasik literally feels like “when [we were] picnicking at the lake”.

Do I need to say pergi berkelah, or is berkelah alone enough?

Both are used:

berkelah – to have a picnic / picnic
pergi berkelah – to go for a picnic

For example:

Kami berkelah di tasik.
We had a picnic at the lake.
Kami pergi berkelah di tasik.
We went for a picnic at the lake.

In your original sentence, berkelah alone is perfectly natural.

Can ketika berkelah di tasik come at the beginning of the sentence?

Yes. Malay allows the time clause to be moved to the front, just like English:

Ketika berkelah di tasik, kami membawa salad buah.
When we were having a picnic at the lake, we brought fruit salad.

This is often used for emphasis on the time/situation. Punctuation: a comma after the first clause is common in writing.

Why is there no plural marking on salad or buah? How do I know it’s not “a fruit salad” vs “fruit salads”?

Malay usually does not mark plural with endings like -s. Number is usually clear from context, or from words like:

satu – one
beberapa – some, several
banyak – many, a lot of

So:

salad buah could be “fruit salad” or “fruit salads”, depending on context.
satu salad buah – one fruit salad
beberapa salad buah – some fruit salads

In your sentence, English most naturally interprets it as “(a) fruit salad” or just “fruit salad” in general.

Can I drop kami and just say Membawa salad buah ketika berkelah di tasik?

You can drop the subject kami in certain contexts, but it changes the feel:

Kami membawa salad buah ketika berkelah di tasik.
Clear: we brought it.
Membawa salad buah ketika berkelah di tasik.
Feels more like a fragment, or part of a longer sentence, e.g. in notes, recipes, or instructions.

In normal full sentences, you usually keep the subject (kami, kita, mereka, etc.) to avoid ambiguity.

How would I say “We will bring fruit salad when we have a picnic at the lake”?

You can add akan to mark future tense:

Kami akan membawa salad buah ketika berkelah di tasik.
We will bring fruit salad when we have a picnic at the lake.

Akan is the usual future marker; without it, the sentence could be present, past, or future depending on context.

Is there any difference between di tasik and di tepi tasik?

Yes:

di tasik – literally “at / in the lake” (but often understood as “at the lake area”)
di tepi tasik – “by the lake / at the lakeside”

For a picnic, di tepi tasik is often more precise and natural:

Kami berkelah di tepi tasik.
We had a picnic by the lake.

However, di tasik is commonly used in everyday speech and is usually understood as “at the lake (area)” rather than literally in the water.