Gaji di syarikat ini rendah.

Malay often drops the copula in simple descriptive sentences. The pattern Noun + (Prepositional Phrase) + Adjective is enough to express “X is Y.” If you want a more formal style, you can insert adalah:

• Gaji di syarikat ini adalah rendah.
  But in everyday speech, that adalah is usually omitted.

Rendah is an adjective meaning “low.” In Malay, adjectives normally follow the noun or noun phrase they modify:

• Noun + Adjective → gaji rendah (“low salary”)
  Here we inserted a location phrase, so the full order is: Noun (Gaji) + Prepositional Phrase (di syarikat ini) + Adjective (rendah).

Yes, that is also grammatically correct and common. Both

• Gaji di syarikat ini rendah.
• Gaji rendah di syarikat ini.
  mean “The salary at this company is low.” The emphasis shifts slightly:
• First version focuses on “salary at this company.”
• Second version highlights “low salary” first.

Demonstratives like “this” (ini) follow the noun they modify in Malay. So you say:

• Noun + ini → syarikat ini (“this company”)
  (not ini syarikat).

Yes. You can attach -nya (“its”) to gaji:

• Gajinya di syarikat ini rendah.
  This literally reads, “Its salary at this company is low.” It’s less common if context already makes clear whose salary you mean, but it’s grammatically valid.

Gaji is treated like a mass noun in Malay; it doesn’t change form for singular/plural. To talk about multiple salaries, you still say gaji. If you need to specify “salaries,” you can add a classifier or context:

• Beberapa gaji (“several salaries”)
• Gaji-gaji is possible but less common.

You can say:

• Kenapa gaji di syarikat ini rendah?
  Here Kenapa means “why.” You keep the same structure and add the question word in front.

Yes. Use tidak before the adjective:

• Gaji di syarikat ini tidak rendah.
  Literally, “The salary at this company is not low.” If you mean “is high” instead of “not low,” you might say:
• Gaji di syarikat ini tinggi.