Στο γκισέ μού ζήτησαν και ένα αποδεικτικό διεύθυνσης μαζί με το δεύτερο δικαιολογητικό.

Στο is the contracted form of σε το, so it means at the or to the, depending on context.

Here, Στο γκισέ means at the counter / at the service desk. Greek very often contracts σε + definite article:

• σε + το = στο
• σε + τη(ν) = στη(ν)
• σε + τους = στους

So this opening phrase simply sets the location: this happened at the counter.

Γκισέ means counter, service window, or desk, especially in places like banks, post offices, public services, and ticket offices.

It is a loanword, originally from French. In everyday Greek, it commonly refers to the place where you stand and speak to an employee behind a desk or window.

So in this sentence, it suggests an official or administrative setting.

Here μού means to me or, more naturally in English with this verb, from me / of me.

With ζητάω / ζητώ, Greek often uses the weak genitive pronoun to show the person from whom something is being requested:

• Μου ζήτησαν ένα έγγραφο = They asked me for a document

You do not use με, because με is the accusative form meaning me as a direct object. In this sentence, the person is not the direct object; the thing requested is the direct object.

Also, many writers would simply write μου. The spelling μού can be used to show a bit more stress or clarity.

Ζήτησαν is the aorist form, third person plural, of ζητάω / ζητώ, so it means they asked.

Greek often leaves the subject unstated if it is clear from context. Here, they refers to the people working at the counter, even though that is not explicitly said.

This is very natural in Greek. English often needs a subject like they, but Greek can simply use the verb form by itself.

Here και is best understood as also or too, not just a simple and.

So the sentence is saying that they requested an additional item:
They also asked me for a proof of address...

That is why και appears right before ένα αποδεικτικό διεύθυνσης. It highlights that this was one more document, in addition to something already mentioned or expected.

Because αποδεικτικό is a neuter noun.

The indefinite article in Greek changes by gender:

• ένας for masculine
• μία / μια for feminine
• ένα for neuter

So:

• ένα αποδεικτικό
• ένα δικαιολογητικό

Both αποδεικτικό and δικαιολογητικό are neuter nouns, which is why you see ένα and το δεύτερο.

Διεύθυνσης is the genitive singular form of διεύθυνση.

Greek often uses the genitive where English uses of. So:

• αποδεικτικό διεύθυνσης = proof of address

This is a very common pattern in Greek noun phrases. The second noun goes into the genitive to show what kind of proof or document it is.

Compare:

• αριθμός τηλεφώνου = phone number
• απόδειξη πληρωμής = proof/receipt of payment
• αποδεικτικό κατοικίας / διεύθυνσης = proof of residence / address

They are similar, but not identical.

Αποδεικτικό means something like proof or evidence of a specific fact.
So αποδεικτικό διεύθυνσης is specifically a document that proves your address.

Δικαιολογητικό is broader and more administrative. It usually means supporting document, required paperwork, or document you must submit.

So in this sentence:

• ένα αποδεικτικό διεύθυνσης = one specific kind of proof
• το δεύτερο δικαιολογητικό = the second required supporting document

Μαζί με means together with, along with, or together with.

So this part means that the proof of address was requested along with the second supporting document.

In other words, the sentence is not talking about two separate moments. It means both items were requested in the same context.

Δεύτερο means second, and it agrees with δικαιολογητικό in gender, number, and case.

Since δικαιολογητικό is neuter singular, the adjective is also neuter singular:

• το δεύτερο δικαιολογητικό

This structure is very normal in Greek:

• το πρώτο έγγραφο
• το νέο διαβατήριο
• το σημαντικό χαρτί

The article το shows that this is a specific document already known in the context.

No, Greek word order is fairly flexible, although some versions sound more natural than others depending on emphasis.

The original sentence puts the location first:

• Στο γκισέ μού ζήτησαν και ένα αποδεικτικό διεύθυνσης μαζί με το δεύτερο δικαιολογητικό.

But you could also say:

• Μου ζήτησαν στο γκισέ και ένα αποδεικτικό διεύθυνσης...
• Και ένα αποδεικτικό διεύθυνσης μού ζήτησαν στο γκισέ...

These alternatives shift the emphasis a little. The original version sounds natural because it first sets the scene, then says what happened there.