Η πωλήτρια στο άλλο κατάστημα είπε ότι μπορώ να το αλλάξω μέσα σε δύο εβδομάδες.

Η πωλήτρια means the saleswoman / the sales assistant.

• η is the feminine singular nominative article, because πωλήτρια is a feminine noun
• it is in the nominative because it is the subject of the sentence: she is the one who said something

So:

• η πωλήτρια = the saleswoman
• η πωλήτρια είπε = the saleswoman said

Πωλήτρια literally means saleswoman. In everyday context, it often means a female shop assistant / sales assistant.

The masculine form is πωλητής.

So a learner may see it translated in different ways depending on context:

• saleswoman
• female salesperson
• shop assistant

στο άλλο κατάστημα means at/in the other store.

Here is the breakdown:

• σε = in / at / to
• το = the
• στο = contracted form of σε + το

So:

• σε το άλλο κατάστημα becomes στο άλλο κατάστημα

This contraction is very common in Greek:

• στο = σε + το
• στη = σε + τη(ν)
• στον = σε + τον

Because of the article.

• στο άλλο κατάστημα = at the other store
• σε άλλο κατάστημα = at another store

The article το makes it definite. So άλλο here is understood as the other one, not just any other one.

Also, άλλο agrees with κατάστημα, which is neuter singular.

Είπε is the aorist form of λέω (to say / tell), and it means said.

This is one of those common Greek verbs whose past form is not fully predictable from the present:

• λέω = I say
• είπα / είπε = I said / he-she-it said

So:

• είπε = she said

The aorist is used here because it refers to a completed past action: she said it at some point in the past.

Ότι means that and introduces the content of what was said.

So:

• είπε ότι... = said that...

In English, that is often optional, and the same is true in Greek in many everyday sentences. You may hear:

• είπε ότι μπορώ...
• είπε μπορώ...

Both can occur, though ότι is very standard and clear.

Because Greek often keeps the tense that matches the meaning of the reported statement, instead of automatically shifting it backward the way English sometimes does.

So:

• είπε ότι μπορώ να το αλλάξω = she said that I can exchange it

This suggests the permission or possibility is still valid now.

If Greek used a past form like μπορούσα, the meaning would change:

• είπε ότι μπορούσα να το αλλάξω = she said that I was able / was allowed to exchange it

That sounds more tied to the past situation.

Modern Greek does not normally use an infinitive the way English does.

So where English says:

• I can change it

Greek says:

• μπορώ να το αλλάξω

Literally, it is more like:

• I can that I change it

But in real grammar terms, να introduces a subjunctive clause. After verbs like μπορώ, Greek normally uses να + verb.

Very common pattern:

• μπορώ να... = can...
• θέλω να... = want to...
• πρέπει να... = must...

Because after να, Greek often uses a subjunctive form, and here the speaker wants a single completed action: exchanging/changing the item one time.

• αλλάζω = I change / I am changing
• να αλλάξω = to change / to exchange, as one complete action

So:

• μπορώ να το αλλάξω = I can exchange it

If you said να το αλλάζω, that would sound more like a repeated or ongoing action, which does not fit this shop-return context.

Yes. Αλλάζω basically means change, but in shopping contexts it often means:

• exchange
• replace
• change for another one

So να το αλλάξω in a store context naturally means to exchange it.

Greek often uses the same verb where English may choose different verbs depending on context.

Το means it here. It is a direct object pronoun, referring to the item being exchanged.

It is neuter singular, so the item is being treated grammatically as a neuter noun, or at least the speaker is using the neuter pronoun for it.

Its position is normal in Greek:

• να το αλλάξω

With these short object pronouns, Greek usually places them before the verb. When να is present, the pronoun goes between να and the verb.

Compare:

• το αλλάζω = I change it
• να το αλλάξω = to change/exchange it

It means within two weeks.

This expression gives a time limit or allowed time period.

• μέσα σε = within / in the space of
• δύο εβδομάδες = two weeks

So the idea is: the exchange is allowed if it happens before the two-week period ends.

This is slightly different from some uses of English in two weeks, which can mean two weeks from now. Greek μέσα σε δύο εβδομάδες clearly means within a period of two weeks.

It is accusative plural.

After the preposition σε, Greek normally uses the accusative. So:

• σε δύο εβδομάδες = in / within two weeks

Also:

• εβδομάδα = week
• εβδομάδες = weeks

Because the number is δύο, the noun is plural.

Yes, Greek word order is fairly flexible, though this sentence is very natural as it stands.

Current order:

• Η πωλήτρια στο άλλο κατάστημα είπε ότι μπορώ να το αλλάξω μέσα σε δύο εβδομάδες.

This is neutral and clear.

Greek can move parts around for emphasis, for example:

• Η πωλήτρια είπε ότι μπορώ να το αλλάξω μέσα σε δύο εβδομάδες στο άλλο κατάστημα would sound odd, because it misplaces the store phrase
• Είπε η πωλήτρια στο άλλο κατάστημα ότι μπορώ... is possible, but less neutral

So yes, word order can vary, but the original sentence is the most straightforward version for ordinary speech.