Μετά το πρωινό σκουπίζω τα ψίχουλα από το πάτωμα της κουζίνας.

Because μετά in the sense of after is followed by the accusative case in Modern Greek.

So:

• μετά το πρωινό = after breakfast
• μετά το μάθημα = after the lesson
• μετά τη δουλειά = after work

Here, το πρωινό is the accusative form of the neuter noun πρωινό.

Usually in everyday Modern Greek, yes, when it is followed by the accusative:

• μετά το φαγητό = after the meal

But you may also see μετά από with a time expression:

• μετά από μία ώρα = after one hour

There is also an older/literary use of μετά meaning with, but that is not what is happening here.

In this sentence, πρωινό means breakfast.

Greek has:

• το πρωί = the morning / in the morning
• το πρωινό = breakfast

So:

• Μετά το πρωινό = after breakfast
  not
• after the morning

Because Greek often drops subject pronouns when they are clear from the verb ending.

• σκουπίζω already means I sweep / I wipe / I brush away

The ending -ω tells you the subject is I.

You could say εγώ σκουπίζω, but that would usually add emphasis, like:

• I’m the one who sweeps up.

The Greek present tense often describes:

• a habitual action
• a routine
• something that generally happens

So σκουπίζω here most naturally means:

• I sweep / wipe up
• I usually sweep / wipe up
• I sweep up after breakfast

It does not have to mean only right now at this moment.

σκουπίζω basically means to wipe, to sweep, or to brush away, depending on context.

In this sentence, with crumbs and the floor, it means something like:

• I sweep up the crumbs
• I brush the crumbs off
• I wipe up the crumbs

It is a very natural verb here because the idea is removing small bits from a surface.

Because ψίχουλα is a neuter plural noun meaning crumbs.

Its basic forms are:

• singular: το ψίχουλο = a crumb
• plural: τα ψίχουλα = crumbs

So in the sentence:

• σκουπίζω τα ψίχουλα = I sweep up the crumbs

The article τα is the neuter plural definite article.

The first letter combination ψ is pronounced like ps together, as in lapse or chips at the end, but here at the beginning of the word.

So:

• ψίχουλα ≈ PSEE-hoo-la

A rough breakdown:

• ψί = psee
• χου = hoo with the Greek χ, a throaty sound
• λα = la

The stress is on the first syllable: ΨΙ-χου-λα.

Because από means from or off, and here it shows where the crumbs are being removed from:

• τα ψίχουλα από το πάτωμα = the crumbs from/off the floor

So the idea is not just that the crumbs are on the floor, but that you are sweeping them off the floor.

Also, το πάτωμα is in the accusative after από, which is normal in Modern Greek.

Not with the same meaning.

• στο πάτωμα = on the floor
• από το πάτωμα = from/off the floor

So:

• Υπάρχουν ψίχουλα στο πάτωμα. = There are crumbs on the floor.
• Σκουπίζω τα ψίχουλα από το πάτωμα. = I sweep the crumbs off the floor.

In your sentence, από το πάτωμα is the correct choice because the verb describes removing them.

Because Greek uses the genitive case to mean of the kitchen.

So:

• το πάτωμα της κουζίνας = the floor of the kitchen = the kitchen floor

Here:

• η κουζίνα = the kitchen
• της κουζίνας = of the kitchen

This is a very common Greek structure:

• η πόρτα του σπιτιού = the door of the house
• το παράθυρο του δωματίου = the window of the room

Greek often expresses this idea with a noun + genitive structure:

• το πάτωμα της κουζίνας

English often prefers an adjective-like noun phrase:

• the kitchen floor

Both mean the same thing. Greek simply builds it differently.

Because Greek uses definite articles very regularly, often more than English does.

In this sentence, each article matches the noun’s:

• gender
• number
• case

For example:

• το πρωινό = neuter singular accusative
• τα ψίχουλα = neuter plural accusative
• το πάτωμα = neuter singular accusative
• της κουζίνας = feminine singular genitive

This may feel heavy to an English speaker, but it is completely normal Greek.

No, Greek word order is fairly flexible.

This sentence is natural as:

• Μετά το πρωινό σκουπίζω τα ψίχουλα από το πάτωμα της κουζίνας.

But you could also hear variations such as:

• Σκουπίζω τα ψίχουλα από το πάτωμα της κουζίνας μετά το πρωινό.
• Τα ψίχουλα τα σκουπίζω από το πάτωμα της κουζίνας μετά το πρωινό.

The original version is very natural because it puts the time phrase first:

• After breakfast, I sweep up the crumbs...

They are:

• μετά = after
• το πρωινό / dictionary noun: πρωινό = breakfast
• σκουπίζω = I sweep / wipe / brush away; dictionary form is the same verb σκουπίζω
• το ψίχουλο = crumb
• από = from, off
• το πάτωμα = floor
• η κουζίνα = kitchen

This is useful because some words appear in changed forms in the sentence, especially της κουζίνας, which comes from η κουζίνα.

It is a time expression telling you when the action happens.

So the sentence breaks down like this:

• Μετά το πρωινό = when? → after breakfast
• σκουπίζω = what do I do? → I sweep / wipe up
• τα ψίχουλα = what do I sweep? → the crumbs
• από το πάτωμα της κουζίνας = from where? → from the kitchen floor

Thinking in these chunks can make Greek sentences much easier to understand.

The stressed syllables are:

• Μετά
• πρωινό
• σκουπίζω
• ψίχουλα
• πάτωμα
• κουζίνας

Greek stress matters, so it is worth learning words together with their accent marks. If you move the stress, the word may sound wrong or even become a different form.

For example:

• σκουπίζω
• κουζίνα
• πρωινό

all need their stress in the correct place.