Για πρωινό τρώω ένα μήλο και μια μπανάνα.

Για πρωινό means for breakfast. In Greek, για often means for, and here it introduces the context of the meal.

Putting Για πρωινό first is natural Greek word order when you want to set the scene first: As for breakfast, I eat... English often does the same thing less explicitly with something like For breakfast, I eat...

In this expression, Greek usually says για πρωινό, not για το πρωινό, when speaking generally about what someone has for breakfast.

So:

• για πρωινό = for breakfast in a general sense
• για το πρωινό = more like for the breakfast, referring to a specific breakfast

In your sentence, the general expression is the natural one.

Here, πρωινό is a noun, meaning breakfast.

It comes from an adjective related to morning, but in modern Greek it is very commonly used as a noun:

• πρωινό = breakfast
• μεσημεριανό = lunch
• βραδινό = dinner/supper

So in this sentence, it is definitely functioning as a noun.

Because Greek verbs already show the subject.

The verb τρώω means I eat. The ending tells you it is first person singular, so Greek usually does not need the pronoun εγώ.

You could say Εγώ τρώω..., but that would add emphasis, as in:

• I eat...
• As for me, I eat...

Without emphasis, Greek normally leaves the pronoun out.

It can mean either, depending on context.

Greek present tense often covers both:

• a general habit: I eat
• something happening now: I am eating

In this sentence, because of Για πρωινό, the most natural interpretation is habitual: this is what the speaker eats for breakfast in general.

So the English meaning is usually I eat an apple and a banana for breakfast.

Because Greek articles must agree with the noun's gender.

• μήλο is neuter, so it takes ένα
• μπανάνα is feminine, so it takes μια

So:

• ένα μήλο = an apple
• μια μπανάνα = a banana

This is one of the basic agreement patterns in Greek.

They are in the accusative case because they are the direct objects of τρώω.

The speaker is eating what?

• ένα μήλο
• μια μπανάνα

Those are therefore objects, so Greek uses the accusative.

However, in these nouns, the accusative looks the same as the nominative:

• μήλο stays μήλο
• μπανάνα stays μπανάνα

So the case is there grammatically, even though the form does not visibly change.

Yes. Greek word order is more flexible than English.

This sentence could also be:

• Τρώω ένα μήλο και μια μπανάνα για πρωινό.

That would still be correct.

The version with Για πρωινό first puts the breakfast context up front. The version with τρώω first sounds a bit more neutral in some contexts. Both are natural.

Both μια and μία are used in modern Greek for the feminine form of a / one.

• μια is extremely common in everyday writing
• μία is also correct and may look a bit more careful or formal

So μια μπανάνα and μία μπανάνα are both acceptable. In your sentence, μια is completely normal.

Because και simply means and, just like in English.

So:

• ένα μήλο και μια μπανάνα = an apple and a banana

Greek does not need anything extra here. It is a straightforward coordination of two nouns.