Learn Hardcore Malay: Restoran itu mempunyai menu panjang yang menarik. - That restaurant has an interesting long menu.

itu is the demonstrative “that.” In Malay, demonstratives ini (this) and itu (that) usually follow the noun they modify.
Restoran itu literally means “that restaurant.” If you omit itu, restoran on its own is indefinite (“a restaurant” or “restaurants” depending on context).

What does mempunyai mean, and can I replace it with ada or punya?

mempunyai = “to have” or “to possess.” It’s more formal or written style.
ada also means “to have/there is,” but it’s colloquial and emphasizes existence:
• Restoran itu ada menu panjang yang menarik.
punya as a main verb (“Restoran itu punya…”) is nonstandard in formal Malay; you’ll hear it in casual speech but it’s better to stick with ada or mempunyai.

Why is yang placed before menarik, and when do I need yang?

yang is a relative marker that links a noun (or noun phrase) to a descriptive element (adjective, clause, etc.). Here, yang menarik means “that is interesting.”
Use yang when you attach an adjective phrase or full clause:
• menu yang berwarna-warni (“menu that is colorful”)
• restoran yang dibuka lewat malam (“restaurant that opens late at night”)
For single, simple adjectives you can often skip yang:
• menu panjang (“long menu”)

In the sentence, why is panjang directly after menu but yang menarik follows? Could I say menu yang panjang menarik?

Malay adjective order is flexible but generally you attach single adjectives right after the noun: menu panjang (“long menu”).
yang menarik is a clause, so it must be introduced by yang.
menu yang panjang menarik would be confusing—readers expect yang to introduce the full descriptor.
If you want two adjectives, you have options:
1. menu panjang dan menarik
2. menu yang panjang dan menarik

Can I drop yang entirely and just say menu panjang dan menarik?

Yes. When you use simple, single-word adjectives joined by dan (“and”), you can omit yang:

Restoran itu mempunyai menu panjang dan menarik.
However, if one descriptor is a full phrase or clause, you need yang for clarity.

There’s no “the” or “a” in the English translation. How do I express “a restaurant” or “the restaurant” in Malay?

Malay has no articles. Definite or demonstrative meaning comes from words like itu (that) or context.
To say “a restaurant,” you can add a numeral classifier: sebuah restoran or simply leave it indefinite: restoran mempunyai…
“The restaurant” is often restoran itu (“that restaurant”) or, if named, Restoran [Name].

How do I pluralize or show quantity of menu or restoran if I want to say “restaurants have long interesting menus”?

Malay nouns are unmarked for plural. Context or numerals indicate number.
To be explicit, you can reduplicate: restoran-restoran (restaurants), menu-menu (menus).
Or use quantifiers: banyak restoran (many restaurants), banyak menu (many menus).

How would I turn this statement into a question: “Does that restaurant have a long interesting menu?”

You can use the question particle Adakah or drop it in casual speech:

How can I intensify panjang or menarik? For example, “a very long menu” or “a really interesting menu.”

Add degree adverbs sangat (very), amat (extremely), terlalu (too):
• menu yang sangat panjang
• menu yang panjang dan sangat menarik
You can also repeat adjectives in colloquial speech for emphasis: panjang-panjang (super long), menarik-menarik (super interesting).

If I want to say “the restaurant’s menu is long and interesting” instead of using mempunyai, how would I do that?

Use a possessive structure or simple predicate:

Both convey “The restaurant’s menu is long and interesting.”