Το επιβατηγό πλοίο έχει γκαράζ οχημάτων.

Because το επιβατηγό πλοίο is a full noun phrase meaning the passenger ship.

• το = the (neuter singular)
• πλοίο = ship
• επιβατηγό = passenger / for carrying passengers

So επιβατηγό adds the idea of what kind of ship it is. Greek often uses an adjective where English might use a noun + noun combination, so passenger ship becomes literally something like passenger-type ship.

Here it is an adjective modifying πλοίο.

It agrees with πλοίο in:

• gender: neuter
• number: singular
• case: nominative

So the pair επιβατηγό πλοίο works as passenger ship.

A learner may also see επιβατηγό used as a noun in other contexts, especially for a passenger vehicle/car, but in this sentence it is describing πλοίο.

το is the definite article, meaning the.

It is used because the subject is definite: the passenger ship.

In this sentence:

• το επιβατηγό πλοίο = the subject
• το matches πλοίο, which is neuter singular

Greek articles must agree with the noun in gender, number, and case.

Because έχει is the 3rd person singular present form of έχω = to have.

The subject is το επιβατηγό πλοίο, which is singular, so Greek uses έχει = it has.

A few present-tense forms of έχω:

• έχω = I have
• έχεις = you have
• έχει = he/she/it has
• έχουμε = we have
• έχετε = you have
• έχουν(ε) = they have

So Το επιβατηγό πλοίο έχει... means The passenger ship has...

Greek can use the indefinite article ένα here, but it is often omitted in sentences with έχω, especially when speaking generally or descriptively.

So:

• έχει γκαράζ οχημάτων = it has a vehicle garage / it has garage space for vehicles
• έχει ένα γκαράζ οχημάτων = it has one / a specific vehicle garage

Both are possible, but the version without ένα sounds more neutral and general.

Because οχημάτων is the genitive plural of όχημα = vehicle.

Greek often uses the genitive where English uses:

• a noun + noun combination, or
• of, or
• sometimes for

So:

• γκαράζ οχημάτων literally = garage of vehicles
• natural English = vehicle garage or garage for vehicles

If Greek used οχήματα, that would be nominative/accusative plural, which would not fit this structure.

Here is the grammar of the whole sentence:

• Το επιβατηγό πλοίο: nominative singular
  This is the subject of the sentence.

• γκαράζ: accusative / direct object function
  It is the thing that the ship has.

• οχημάτων: genitive plural
  It depends on γκαράζ and means of vehicles / for vehicles.

One small detail: γκαράζ is a loanword and does not visibly change form here, so its case is understood from its function in the sentence rather than from a special ending.

Because γκαράζ is a loanword and is usually treated as indeclinable in Modern Greek.

That means the word itself often stays the same, while the article or context shows its role.

For example:

• το γκαράζ = the garage
• του γκαράζ = of the garage
• τα γκαράζ = the garages

So in your sentence, γκαράζ stays γκαράζ even though it functions as the object of έχει.

Yes. Greek word order is more flexible than English word order.

The neutral, straightforward order here is:

• Το επιβατηγό πλοίο έχει γκαράζ οχημάτων.
• Subject + Verb + Object

That is the most natural order for a learner to use.

Other orders are possible for emphasis, but they sound more marked. For example, moving γκαράζ οχημάτων to the front would emphasize the garage rather than simply state the fact.

So the given order is the best default pattern.

A rough pronunciation guide is:

To epivatigó plío échi gkaráz ochimáton

A few helpful notes:

• γκαράζ begins with γκ, which at the start of a word is usually pronounced like a hard g
• χ in έχει is not an English sound; before ι/ε it is softer, somewhat like the ch in German ich
• χ in οχημάτων is a stronger sound, more like the ch in Bach
• stress falls on the accented syllable:
  • επιβατηγό
  • πλοίο
  • έχει
  • γκαράζ
  • οχημάτων

So if you focus on the stressed syllables, your pronunciation will already sound much more natural.