Ο ζαχαροπλάστης φτιάχνει πολύ καλό τσουρέκι.

Ο is the masculine singular definite article: the.

So ο ζαχαροπλάστης means the pastry chef.

Greek uses the definite article very often, including with people, jobs, and subjects of sentences. So where English might sometimes leave an article out in other contexts, Greek often keeps one.

A few clues help:

• ο marks it as nominative masculine singular, which is the usual case for the subject.
• φτιάχνει is 3rd person singular, so it matches a singular subject.
• In normal Greek word order, the subject often comes before the verb.

So ο ζαχαροπλάστης = the pastry chef is the one doing the action.

Φτιάχνει is:

• present tense
• 3rd person singular
• from the verb φτιάχνω = make, prepare, create, sometimes fix

So φτιάχνει means he/she/it makes or is making, depending on context.

It can mean either.

Greek present tense often covers both:

• he makes
• he is making

The exact English translation depends on context. If this is just a general statement, makes is natural. If you are describing what is happening right now, is making is natural.

Here πολύ means very, so it is being used as an adverb.

It modifies καλό:

• πολύ καλό = very good

When πολύ means very, it does not change form.

Compare:

• πολύ καλό τσουρέκι = very good tsoureki
• πολλή ζάχαρη = a lot of sugar / much sugar

In the second example, the word is acting more like an adjective/quantifier, so the form changes.

Because καλό has to agree with τσουρέκι.

Τσουρέκι is:

• neuter
• singular

So the adjective must also be:

• neuter
• singular

That gives:

• καλός = masculine
• καλή = feminine
• καλό = neuter

Since τσουρέκι is neuter, Greek uses καλό.

It is the direct object, so it is in the accusative.

The pastry chef is making what?
→ τσουρέκι

A useful thing to know: for many neuter singular nouns in Greek, the nominative and accusative forms are the same. So τσουρέκι looks the same whether it is a subject or an object.

Because Greek can leave the object indefinite or general.

So:

• Ο ζαχαροπλάστης φτιάχνει πολύ καλό τσουρέκι.
  = The pastry chef makes very good tsoureki.

This sounds like a general statement about what he makes, or about the quality of his product.

If you add an article, the meaning changes:

• το πολύ καλό τσουρέκι = the very good tsoureki
  specific
• ένα πολύ καλό τσουρέκι = a very good tsoureki
  one item, indefinite

Because in Greek, adjectives often come before the noun, especially in everyday speech.

So:

• πολύ καλό τσουρέκι = normal and natural

Greek word order with adjectives is somewhat flexible, but putting the adjective before the noun is very common here.

No, Greek word order is more flexible than English word order.

The neutral, straightforward order here is:

• Ο ζαχαροπλάστης φτιάχνει πολύ καλό τσουρέκι.

But Greek can move things around for emphasis, for example:

• Πολύ καλό τσουρέκι φτιάχνει ο ζαχαροπλάστης.

That puts more focus on πολύ καλό τσουρέκι.

Even when the order changes, the cases and verb forms help show who is doing what.

A rough pronunciation guide is:

o za-cha-ro-PLAS-tis FTYAH-khnee po-LI ka-LO tsoo-REH-kee

A few useful notes:

• ζ sounds like z
• χ is a throat sound, like German ch in Bach
• τσ sounds like ts
• the written accent mark shows the stressed syllable:
  • ζαχαροπλάστης
  • φτιάχνει
  • πολύ
  • καλό
  • τσουρέκι

Very often, yes: nouns ending in -ι are commonly neuter in Modern Greek.

So το τσουρέκι is a neuter noun.

That is why any adjective agreeing with it must also be neuter:

• καλό τσουρέκι
• not καλός τσουρέκι

Usually φτιάχνει is the better choice here.

• φτιάχνω = make / prepare
• κάνω = do / make, but more general

Greek often prefers φτιάχνω when talking about preparing food or making something concrete. So φτιάχνει πολύ καλό τσουρέκι sounds more natural.