Ο ίδιος πωλητής με θυμήθηκε και μου χαμογέλασε όταν μπήκα ξανά στο μαγαζί.

Here ο ίδιος πωλητής means the same salesperson / the same salesman.

A very useful distinction:

• ο ίδιος πωλητής = the same salesperson
• ο πωλητής ο ίδιος = the salesperson himself

So in this sentence, ίδιος is not himself. It means this was the same person as before.

Greek uses the definite article very often, and with ίδιος it helps create the meaning the same.

So:

• ο ίδιος πωλητής = the same salesperson
• without the article, the phrase would not sound the same and could feel incomplete or unnatural in this context

The article also shows that the speaker and listener can identify which salesperson is being talked about.

Yes, it looks like a middle/passive form, but θυμάμαι is one of those Greek verbs that has middle/passive endings but active meaning.

So:

• θυμάμαι = I remember
• θυμήθηκε = he/she remembered

In this sentence, με θυμήθηκε means he remembered me or, very naturally in context, he recognized me from before.

So even though the form looks passive to an English speaker, the meaning here is active.

They are both object pronouns, but they do different jobs.

• με = me as a direct object
• μου = to me / at me / for me as an indirect object

In the sentence:

• με θυμήθηκε = he remembered me
• μου χαμογέλασε = he smiled at me

So the change from με to μου depends on what each verb requires.

Because χαμογελάω / χαμογελώ works like smile at someone.

So Greek says:

• μου χαμογέλασε = he smiled at me

Using με here would not be correct for standard Greek, because χαμογελάω does not take a direct object in this meaning.

You can think of μου here as meaning something like toward me or at me.

All three are in the aorist, which here corresponds to the simple past in English.

• θυμήθηκε = remembered
• χαμογέλασε = smiled
• μπήκα = I entered / I went in

The aorist presents each action as a whole, as a single event:

• he remembered me
• he smiled at me
• I went in again

This is the normal tense for narrating completed past events.

Because μπήκα presents the action as one completed event: when I went in / when I entered.

Compare:

• όταν μπήκα = when I entered / when I went in
• όταν έμπαινα = when I was going in / while I was entering

In this sentence, the seller’s remembering and smiling happened at the moment of entry, so the aorist μπήκα is the natural choice.

Here ξανά means again: the speaker entered the shop one more time.

So:

• μπήκα ξανά στο μαγαζί = I went into the shop again

Yes, πάλι can also sometimes mean again, but ξανά is especially clear for repetition of an action.

Very roughly:

• ξανά = again, once more
• πάλι = again, but also back, still, or sometimes adds emotional emphasis depending on context

In this sentence, ξανά is a very natural choice.

στο is a contraction of:

• σε
  • το → στο

So:

• στο μαγαζί = in/into the shop

This contraction is extremely common in Greek:

• σε + τον → στον
• σε + την often stays στη(ν)
• σε + το → στο

So yes, it is written as one word, but it comes from two parts.

With μπαίνω, σε + accusative usually gives the meaning into.

So:

• μπήκα στο μαγαζί = I went into the shop / I entered the shop

English often distinguishes in and into more strictly than Greek does. Greek σε covers several ideas that English splits up.

Here, because the verb is μπαίνω (enter / go in), the meaning is clearly into the shop, not just in the shop.

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

The verb ending already tells you the subject:

• μπήκα = I entered

So adding εγώ would only be necessary for emphasis or contrast:

• εγώ μπήκα ξανά = I was the one who went in again

Without special emphasis, Greek normally just uses the verb.

Greek word order is more flexible than English word order.

The sentence as written is natural and neutral:

• Ο ίδιος πωλητής με θυμήθηκε και μου χαμογέλασε όταν μπήκα ξανά στο μαγαζί.

But Greek could move parts around for emphasis, for example:

• Με θυμήθηκε ο ίδιος πωλητής...
• Όταν μπήκα ξανά στο μαγαζί, ο ίδιος πωλητής...

The basic meaning stays the same, but the focus changes slightly.

The original version puts ο ίδιος πωλητής first, which gives the subject a bit of prominence.

Yes. μαγαζί is a very common everyday word for shop/store.

It is natural and conversational. Depending on context, it can mean:

• shop
• store
• business
• place

A more formal or official word is κατάστημα.

So:

• μαγαζί = everyday, common speech
• κατάστημα = more formal

In this sentence, μαγαζί sounds completely natural.