Όταν έχει ήλιο, κάθομαι στο μπαλκόνι και πίνω καφέ.

It literally means when, but in this sentence it is best understood as whenever.

The sentence describes a repeated habit, not one single event:

• Όταν έχει ήλιο, κάθομαι... = Whenever it’s sunny, I sit...

Greek often uses όταν with the present tense for this kind of general truth or routine.

Because έχει ήλιο is a very common Greek way to talk about sunny weather.

Greek often uses έχει + a weather noun:

• έχει ζέστη = it’s hot
• έχει κρύο = it’s cold
• έχει αέρα = it’s windy
• έχει ήλιο = it’s sunny

So even if the literal wording feels strange in English, it is completely natural in Greek.

Greek often does not use a dummy subject like English it in weather expressions.

English says:

• it’s sunny
• it’s raining

Greek can simply say:

• έχει ήλιο
• βρέχει

So nothing is missing. Greek just does not need the extra subject here.

Because ήλιο is the accusative form of ήλιος.

• ο ήλιος = the sun as a subject
• ήλιο = sun as a direct object

In έχει ήλιο, the noun is the object of έχει, so Greek uses the accusative.

Some Greek verbs have middle/passive-type endings but active meanings. Κάθομαι is one of them.

So although it looks different from verbs like πίνω, it simply means:

• I sit
• I am sitting

You just learn it as its normal form:

• κάθομαι
• κάθεσαι
• κάθεται

It can mean either, depending on context.

Greek present tense often covers both:

• a general/habitual meaning: I sit
• a continuous meaning: I am sitting

In this sentence, because it describes a habit, English usually translates it as I sit:

• When it’s sunny, I sit on the balcony...

Στο is the contracted form of σε + το.

So:

• σε το μπαλκόνι becomes στο μπαλκόνι

It means in/on/at the, depending on context. Here it means:

• στο μπαλκόνι = on the balcony

This contraction is standard in modern Greek.

Because μπαλκόνι is a neuter noun.

Its basic article is:

• το μπαλκόνι = the balcony

After σε, everyday modern Greek still uses the accusative form of the article, so:

• σε + το = στο
• στο μπαλκόνι = on the balcony

At the beginning of a Greek word, μπ is usually pronounced like b.

So μπαλκόνι is pronounced roughly bal-KO-ni.

Also, the accent mark shows which syllable is stressed:

• μπαλκόνι

Because Greek usually leaves out subject pronouns when they are not needed.

The verb ending already shows the subject:

• κάθομαι = I sit / I am sitting
• πίνω = I drink / I am drinking

You would add εγώ only for emphasis or contrast:

• Εγώ κάθομαι στο μπαλκόνι, όχι μέσα.

Because καφέ is the accusative form, and it is the direct object of πίνω.

• ο καφές = nominative
• τον καφέ = accusative

Since you drink coffee, Greek uses the object form:

• πίνω καφέ

Greek often leaves out the article with food and drink when speaking in a general way.

So:

• πίνω καφέ = I drink coffee / I drink some coffee

If you wanted to be more specific, you could say:

• πίνω έναν καφέ = I’m drinking a coffee
• πίνω τον καφέ μου = I’m drinking my coffee

Because the sentence begins with a subordinate clause.

Greek normally separates an introductory when-clause with a comma:

• Όταν έχει ήλιο, κάθομαι στο μπαλκόνι...

English often does the same:

• When it’s sunny, I sit on the balcony...

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

The given sentence is the most neutral and natural version:

• Όταν έχει ήλιο, κάθομαι στο μπαλκόνι και πίνω καφέ.

But Greek could change the order for emphasis:

• Όταν έχει ήλιο, πίνω καφέ και κάθομαι στο μπαλκόνι.

That would still be understandable, but it may shift the focus slightly.

Yes. Και simply links the two actions:

• κάθομαι στο μπαλκόνι
• πίνω καφέ

So:

• κάθομαι στο μπαλκόνι και πίνω καφέ = I sit on the balcony and drink coffee

It is the ordinary coordinating word and.