Η ανυπομονησία του παιδιού ήταν μεγάλη, αλλά και η αφοσίωσή του στο παζλ φαινόταν.

Του παιδιού is the genitive singular of το παιδί.

In this sentence, it shows possession or association, so it means of the child or the child's. Greek often uses the genitive where English would use 's:

• η ανυπομονησία του παιδιού = the child's impatience

A learner may expect something different because παιδί is neuter, but this is completely normal:

• nominative: το παιδί
• genitive: του παιδιού

So του here is not his yet; it is the genitive article meaning of the.

That του is a possessive clitic pronoun, meaning his, its, or more naturally here the child's.

So:

• η αφοσίωσή του = his devotion / the child's devotion

Greek often does this instead of repeating the full noun phrase again. So after saying του παιδιού once, the sentence naturally continues with του rather than repeating του παιδιού.

This is very common:

• το βιβλίο του = his book
• η μητέρα της = her mother

Here, the του refers back to το παιδί.

Because it is followed by an enclitic: του.

The basic noun is:

• η αφοσίωση

But when an enclitic like μου, σου, του, της, μας, σας, τους follows, Greek often adds an extra written accent to show the correct stress pattern:

• η αφοσίωσή του

This is a spelling rule, not a different word or case. You will see the same kind of thing in examples like:

• ο άνθρωπός μου
• η φωνή της sometimes without extra accent depending on stress pattern, but with longer words the added accent is especially common and important

So αφοσίωσή is just αφοσίωση written with the extra accent because of του.

Because the adjective must agree with ανυπομονησία, which is feminine singular.

• η ανυπομονησία = feminine singular
• therefore μεγάλη = feminine singular

Greek adjectives change form to match the noun in gender, number, and case.

So:

• μεγάλος = masculine
• μεγάλη = feminine
• μεγάλο = neuter

Here, μεγάλη does not literally have to mean big. In context it means something like great, strong, or intense.

Αλλά και means something like but also or and also.

It adds a second idea while keeping some contrast:

• first idea: the child's impatience was great
• second idea: the child's devotion to the puzzle was also noticeable

So αλλά και is not a harsh contradiction. It is more like:

• but at the same time
• but also

This combination is very common in Greek when the speaker wants to add a second important point.

Because Greek normally repeats the article when two separate noun phrases are coordinated.

So Greek prefers:

• η ανυπομονησία ..., αλλά και η αφοσίωσή ...

rather than leaving the second article out.

This helps make the structure clear and balanced. It also emphasizes that these are two distinct things being talked about:

1. η ανυπομονησία
2. η αφοσίωση

English can often skip repeated articles more easily, but Greek usually keeps them.

Because φαίνομαι is one of those Greek verbs that has middle/passive-style forms but an active meaning.

• φαίνομαι = I appear / I seem / I am visible
• imperfect: φαινόταν = was appearing / seemed / was visible

So even though φαινόταν ends like a middle/passive form, here it does not mean a true passive like was being shown. It means:

• was apparent
• could be seen
• seemed evident

This kind of verb is very common in Greek, so it is worth getting used to the idea that form and meaning do not always match the way an English speaker expects.

Because the two verbs express slightly different ideas.

• ήταν μεγάλη = was great
  This directly states a quality.

• φαινόταν = was visible / was apparent / could be seen
  This presents the quality as something observable.

So the sentence is not just listing two facts in exactly the same way. It is doing something a bit more nuanced:

• the impatience is stated directly
• the devotion is described as something that showed itself outwardly

Also, both verbs are in the imperfect, which is very common in Greek narrative when describing an ongoing situation in the past.

Στο is the contraction of:

• σε + το = στο

So στο παζλ literally means to the puzzle, at the puzzle, or on the puzzle, depending on context.

Here it goes with αφοσίωση:

• αφοσίωση σε κάτι = devotion to something

So in this sentence, στο παζλ is best understood as:

• to the puzzle

Usually no. Παζλ is an indeclinable loanword, so its form typically stays the same.

That means Greek shows case mainly through the article:

• το παζλ
• του παζλ
• στο παζλ

This is common with some borrowed words in modern Greek. So if you were wondering why the noun itself does not seem to change, that is the reason.

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

This sentence uses a natural, balanced order for written narration:

• Η ανυπομονησία του παιδιού ήταν μεγάλη, αλλά και η αφοσίωσή του στο παζλ φαινόταν.

But Greek could move things around for emphasis. For example, a speaker might front an adjective or another phrase if they want to stress it more.

Even so, the version you have is very natural because it sets up a neat parallel:

• η ανυπομονησία ...
• η αφοσίωσή ...

with each idea getting its own place in the sentence.