Τώρα που λειτουργεί ο τροχός αγγειοπλαστικής, αρχίζει η διαμόρφωση.

Here Τώρα που means now that.

It does not just mean a simple now. The whole phrase introduces a clause that gives the condition or situation under which the next action happens:

• Τώρα που λειτουργεί ο τροχός αγγειοπλαστικής = Now that the pottery wheel is working

In this use, που is functioning like a conjunction, not like the relative pronoun who/which/that.

λειτουργεί is the 3rd person singular present of λειτουργώ.

Here it means something like:

• works
• is functioning
• is operating
• is running

So ο τροχός λειτουργεί means the wheel is working / operating.

Greek uses the present tense here because it describes a current, ongoing state: the wheel is now in operation.

So the logic is:

• Now that the wheel is working
• the shaping begins

This is very natural in Greek, just as it is in English.

Literally, it is the wheel of pottery-making.

A more natural English translation would be:

• the pottery wheel
• the potter’s wheel

Greek often expresses this kind of idea with a noun + genitive noun structure, where English might prefer an adjective or a compound noun.

αγγειοπλαστικής is in the genitive singular.

The base noun is η αγγειοπλαστική, and here the genitive shows a relationship like:

• type
• purpose
• field
• association

So τροχός αγγειοπλαστικής means something like:

• wheel for pottery
• wheel used in pottery
• pottery wheel

This is a very common Greek pattern.

Because the phrase is being used in a classifying way.

Greek often omits the article in this kind of noun phrase when the second noun identifies the type or function of the first:

• τροχός αγγειοπλαστικής = pottery wheel
• not necessarily the wheel of the pottery

If you added an article, the meaning could become more specific or context-dependent.

The subject is η διαμόρφωση.

So the structure is:

• αρχίζει = begins
• η διαμόρφωση = the shaping / the forming

Literally: begins the shaping
But in natural English: the shaping begins

This can confuse English speakers because Greek often allows the verb to come before the subject, especially in narrative or descriptive style.

Greek uses the definite article more often than English does, especially with:

• abstract nouns
• general processes
• clearly identifiable stages in a procedure

So η διαμόρφωση can mean:

• the shaping
• the forming stage
• the process of shaping

Even if English would sometimes just say shaping, Greek often prefers η διαμόρφωση.

διαμόρφωση is a noun meaning:

• shaping
• forming
• formation
• modelling

In this context, it refers to the stage where the material is being given its form, so shaping or forming is the most natural translation.

It comes from the verb διαμορφώνω, meaning to shape, to form, or to configure.

Sometimes, but the meaning would shift a little.

• Τώρα που = now that
  Focuses on the present situation as the reason or basis for what follows.

• όταν = when
  More neutral and purely temporal.

• αφού = since / after
  Can sound more causal or imply that something has already been established.

So Τώρα που λειτουργεί ο τροχός... is especially good if the idea is:

• the wheel is now working
• and because of that, the next stage can begin

Because the sentence begins with a subordinate clause:

• Τώρα που λειτουργεί ο τροχός αγγειοπλαστικής

and then moves to the main clause:

• αρχίζει η διαμόρφωση

Greek commonly uses a comma to separate that opening clause from the main statement, just as English often does with an introductory clause.