Learn Hardcore Malay: Bagasi beratnya memerlukan diskaun khusus di kaunter bayaran. - His/Her heavy luggage requires a special discount at the payment counter.

It marks berat (“heavy”) as a definite noun – “the heaviness” or “the weight.”
It also functions like a third-person possessive – “its heavy baggage.”
So bagasi beratnya literally means “its baggage’s weight” or more idiomatically “its heavy baggage.” You could rephrase with a relative clause: Bagasi yang berat memerlukan… (“Baggage that is heavy requires…”).

Could we drop -nya and just say Bagasi berat memerlukan diskaun khusus…?

Yes.
• Bagasi berat memerlukan… means “Heavy baggage requires…” in a general sense (indefinite).
• Bagasi beratnya memerlukan… refers to a specific baggage’s weight (definite/possessive).

Why is the adjective khusus placed after the noun diskaun?

Malay normally follows the pattern Noun + Adjective.
• diskaun khusus = “discount special” (i.e. “special discount”).
In English it’s Adjective + Noun, but in Malay it’s reversed.

How is the verb memerlukan formed and what do its parts mean?

memerlukan breaks down as:
• meN- (active verb prefix)
• perlu (root meaning “need”)
• -kan (suffix often used to make verbs transitive or causative)Put together, = “to require,” “to need something.”