Αυτό το Σάββατο, αν δεν βρέχει, πάμε στην αγορά και μετά στο πάρκο.

Because Σάββατο is a neuter noun in Greek: το Σάββατο = Saturday.

So this Saturday becomes:

• αυτό = this (neuter form)
• το = the (neuter article)
• Σάββατο = Saturday

So Αυτό το Σάββατο literally looks like this the Saturday, which is the normal Greek pattern with demonstratives.

Also, time expressions like this Saturday, this week, that day are often used without a preposition in Greek.

It is functioning as a time expression, which in Greek is often in the accusative.

But here you do not see a change because Σάββατο is neuter, and in the singular the nominative and accusative look the same:

• το Σάββατο = nominative
• το Σάββατο = accusative

A clearer comparison is with a feminine day:

• αυτή η Κυριακή = this Sunday as a subject
• αυτή την Κυριακή = this Sunday as a time expression

So in your sentence, the form is doing accusative-type work even though it looks unchanged.

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

Here πάμε means:

• we go
• we’re going
• sometimes let’s go, depending on context

The ending -με tells you the subject is we, so εμείς is not necessary.

If you did say εμείς πάμε, it would usually add emphasis, something like we are the ones going.

Greek often uses the present tense for a planned or arranged future action, just like English does in sentences such as We’re going to the market on Saturday.

So πάμε here means something like:

• we’re going
• we’re going to go
• we go in the sense of a planned action

You could also say θα πάμε, which makes the future meaning more explicit. But πάμε is very natural when talking about plans.

Grammatically, yes: πάμε can also mean let’s go.

But context decides the meaning.

In this sentence, because you have:

• a time phrase: Αυτό το Σάββατο
• a condition: αν δεν βρέχει

the natural meaning is we’re going / we’ll go, not a direct suggestion like let’s go.

Compare:

• Πάμε! = Let’s go!
• Αυτό το Σάββατο πάμε στην αγορά. = This Saturday we’re going to the market.

This is a very common learner question, because both are possible, but they are not exactly the same.

• αν δεν βρέχει = if it isn’t raining
• αν δεν βρέξει = if it doesn’t rain

The version with βρέχει focuses on the weather as an ongoing situation at that time: if it’s not raining.

The version with βρέξει sounds more like whether the rain event happens at all: if it doesn’t rain.

So the sentence you have feels a bit like: This Saturday, if the weather isn’t rainy / if it’s not raining, we’re going...

Because Greek weather verbs are usually impersonal.

So:

• βρέχει = it’s raining
• χιονίζει = it’s snowing

Greek does not need a separate dummy subject like English it.

So δεν βρέχει simply means it isn’t raining.

They are contracted forms of σε + article.

• σε + την = στην
• σε + το = στο

So:

• στην αγορά = to the market / at the market
• στο πάρκο = to the park / at the park

After a verb of motion like πάμε, the meaning is naturally to:

• πάμε στην αγορά = we go to the market
• πάμε στο πάρκο = we go to the park

Because the two nouns have different grammatical gender:

• η αγορά = the market → feminine
• το πάρκο = the park → neuter

So the form of σε + the changes:

• feminine singular: στην
• neuter singular: στο

For comparison:

• masculine singular is usually στον

So Greek articles and preposition combinations must agree with the gender of the noun.

Here μετά means then or afterwards.

So:

• πάμε στην αγορά και μετά στο πάρκο

means:

• we go to the market and then to the park

In this sentence, μετά is functioning as an adverb, not as part of a phrase like after the park.

Because Greek often leaves out repeated words when they are already understood.

The full version could be:

• πάμε στην αγορά και μετά πάμε στο πάρκο

But Greek very naturally shortens that to:

• πάμε στην αγορά και μετά στο πάρκο

The second πάμε is understood from the first one.

English does the same sometimes:

• We’re going to the market and then to the park.

No, Greek word order is fairly flexible.

The given order:

• Αυτό το Σάββατο, αν δεν βρέχει, πάμε στην αγορά και μετά στο πάρκο.

puts the focus first on when, then on the condition, and then on the main action.

Other orders are possible, for example:

• Αν δεν βρέχει αυτό το Σάββατο, πάμε στην αγορά και μετά στο πάρκο.

That said, the original sentence sounds very natural and well organized.

Because αν δεν βρέχει is an inserted conditional clause.

The commas help separate:

• the time frame: Αυτό το Σάββατο
• the condition: αν δεν βρέχει
• the main statement: πάμε στην αγορά και μετά στο πάρκο

In everyday writing, punctuation can vary a little, but these commas make the sentence easier to read and clearly show its structure.