این رستوران خیلی گران است.

Word by word:

• این = this
• رستوران = restaurant
• خیلی = very
• گران = expensive
• است = is

So the sentence is literally this restaurant very expensive is.

In Persian, the verb usually comes at the end of the sentence. That includes the verb to be in formal writing.

So:

• این رستوران خیلی گران است
  = This restaurant is very expensive

A natural English speaker may expect is in the middle, but Persian normally puts it last.

Persian does not have a direct equivalent of the English definite article the.

So رستوران can mean:

• restaurant
• the restaurant
• sometimes a restaurant

The context tells you which meaning is intended. In این رستوران, the word این already makes it specific, so the meaning is clearly this restaurant.

Yes, این commonly means this.

It comes before the noun:

• این رستوران = this restaurant
• این کتاب = this book

The opposite is آن = that:

• آن رستوران = that restaurant

In everyday speech, you may also hear اون for that.

خیلی is an adverb meaning very, so it comes before the adjective it modifies:

• خیلی گران = very expensive
• خیلی خوب = very good
• خیلی بزرگ = very big

This is similar to English, where very also comes before the adjective.

Yes, گران is an adjective meaning expensive.

In this sentence, it is part of the predicate:

• این رستوران خیلی گران است
• literally: This restaurant very expensive is

But when an adjective comes directly with a noun, Persian often places it after the noun:

• رستوران گران = an expensive restaurant

So Persian adjectives often follow the noun, unlike English.

است is the formal written form of is.

In everyday speech, people often say:

• این رستوران خیلی گرونه

That final ـه sound is the colloquial equivalent of است here.

You may also hear هست in some contexts, but for simple everyday sentences like this, spoken Persian often drops down to the shorter colloquial form.

So:

• formal: این رستوران خیلی گران است
• spoken: این رستوران خیلی گرونه

A careful pronunciation is roughly:

• in restorân kheyli gerân ast

A more natural spoken version is often:

• in restorân kheyli gerune

A few notes:

• این sounds like in
• خیلی sounds roughly like kheyli
• گران sounds roughly like gerân
• in conversation, گران است often becomes گرونه

This is a very common spoken reduction in Persian.

Formal:

• گران است

Colloquial:

• گرانه or more commonly in modern pronunciation گرونه

This kind of change happens often with adjective + است in spoken Persian:

• خوب است → خوبه = it is good
• بزرگ است → بزرگه = it is big
• گران است → گرونه = it is expensive

So if you learn the formal sentence first, that is good, but you should also recognize the spoken version.

To make it negative, you use نیست for is not:

• این رستوران خیلی گران نیست
• This restaurant is not very expensive

In spoken Persian, you may hear:

• این رستوران خیلی گرون نیست

So:

• است = is
• نیست = is not

In Persian, a yes/no question can often be made just by using rising intonation in speech:

• این رستوران خیلی گران است؟
• Is this restaurant very expensive?

In informal spoken Persian:

• این رستوران خیلی گرونه؟

Persian does not always need a separate helping verb like English is at the beginning.

Yes. خیلی often means very, but depending on context it can also mean a lot or much.

Examples:

• خیلی گران است = It is very expensive
• خیلی کار می‌کند = He/She works a lot

In your sentence, because it comes before the adjective گران, it clearly means very.

Sometimes, yes, but است is the standard form in this sentence.

• است is the regular written copula here.
• هست often appears when you want a little more emphasis, or in certain patterns, but it is not the most neutral choice for this exact sentence.

So for a learner, the safest standard version is:

• این رستوران خیلی گران است

And the common spoken version is:

• این رستوران خیلی گرونه

In everyday spoken Persian, the most natural version is usually:

• این رستوران خیلی گرونه

That is what you are likely to hear in conversation.

So it is useful to know both:

• Formal/written: این رستوران خیلی گران است
• Natural spoken: این رستوران خیلی گرونه