Προτού δώσει έγκριση, η υπάλληλος έλεγξε αν το διαβατήριο ήταν έγκυρο και όχι ληγμένο.

Προτού means before. In this sentence, it introduces a time clause:

Προτού δώσει έγκριση = Before she gave approval / Before approving

It is very similar to πριν. In many contexts, πριν and προτού can both be used, though προτού often sounds a bit more formal or written.

For example:

• Πριν δώσει έγκριση...
• Προτού δώσει έγκριση...

Both are natural.

Because after προτού Greek normally uses the subjunctive, not the ordinary past indicative.

So:

• έδωσε = she gave (simple past, indicative)
• δώσει = subjunctive form, used after words like προτού, να, αν in certain structures

Here, προτού δώσει literally means something like before she should give / before giving, but in natural English it is translated as before she gave or before giving approval.

This is very common in Greek:

• Πριν φύγω... = Before I leave / Before leaving
• Προτού μιλήσει... = Before he/she speaks

Because προτού can be followed either by:

• να + subjunctive, or
• directly by the subjunctive form without να

So both are possible:

• Προτού δώσει έγκριση
• Προτού να δώσει έγκριση

The version without να is very common and natural.

The subject of δώσει is understood to be η υπάλληλος.

Greek often leaves out subject pronouns or repeated subjects when they are clear from context. Here the sentence means:

Before giving approval, the employee checked...

So Greek does not need to repeat η υπάλληλος inside the first clause. It is understood that the same person both:

• would give approval
• checked the passport

In Greek, noun endings do not always match the gender patterns an English speaker may expect.

Η υπάλληλος is a feminine noun here because of the article η and the meaning/context. Some Greek nouns ending in -ος are feminine.

So:

• η υπάλληλος = the female employee / the clerk / the official

If the context were male, you could also have:

• ο υπάλληλος = the male employee

So υπάλληλος can refer to either gender; the article tells you which one is meant.

Yes. They are both past forms, but they express different kinds of past meaning.

• έλεγξε is aorist: a completed action
  = she checked
• ήταν is imperfect of είμαι: a state or ongoing situation in the past
  = it was

So Greek is saying:

• she performed one completed action: checking
• at that time, the passport had a certain state: it was valid and not expired

This is a very typical contrast in Greek:

• aorist for a single completed event
• imperfect for background, condition, or ongoing state

Here αν means whether, not a condition like if in if it rains.

In this sentence:

• έλεγξε αν το διαβατήριο ήταν έγκυρο
  means
• she checked whether the passport was valid

This is an indirect yes/no question.

Compare:

• Δεν ξέρω αν έρχεται. = I don’t know whether he’s coming.
• Έλεγξε αν ήταν σωστό. = She checked whether it was correct.

So this αν introduces something being checked, asked, or known.

It is the subject of ήταν.

The clause is:

• το διαβατήριο ήταν έγκυρο
• the passport was valid

That means:

• το διαβατήριο = subject
• ήταν = was
• έγκυρο = predicate adjective/complement

This can be confusing because in neuter nouns, the nominative and accusative forms often look the same:

• το διαβατήριο can be either subject or object depending on the sentence

Here, because it goes with ήταν, it is the subject.

Because they agree with το διαβατήριο, which is:

• neuter
• singular

So:

• το διαβατήριο = neuter singular
• έγκυρο = valid, neuter singular
• ληγμένο = expired, neuter singular

This is normal adjective agreement in Greek.

Compare:

• το διαβατήριο ήταν έγκυρο
• η άδεια ήταν έγκυρη
• ο τίτλος ήταν έγκυρος

Same adjective, different endings to match gender.

Because όχι is negating the adjective phrase, not introducing a whole new verb clause.

The structure is:

• ήταν έγκυρο και όχι ληγμένο
• literally: it was valid and not expired

Greek is keeping ήταν only once and linking two adjective complements:

• έγκυρο
• όχι ληγμένο

You could also say:

• το διαβατήριο ήταν έγκυρο και δεν ήταν ληγμένο

But that repeats the verb and sounds a bit heavier. The version in the sentence is smoother and more compact.

Because Greek often omits the article with abstract or non-specific objects, especially in expressions like give approval.

So:

• δώσει έγκριση = give approval / grant approval

This does not mean a specific previously mentioned approval, so την έγκριση is not needed.

Compare:

• πήρε άδεια = he got permission
• έδωσε σημασία = she paid attention
• δώσει έγκριση = give approval

Using no article often makes the phrase more general or idiomatic.

Yes. Greek word order is fairly flexible.

This sentence could also be rearranged, for example:

• Η υπάλληλος έλεγξε αν το διαβατήριο ήταν έγκυρο και όχι ληγμένο προτού δώσει έγκριση.

That still means the same thing:

• The employee checked whether the passport was valid and not expired before giving approval.

The original version puts Προτού δώσει έγκριση first, which foregrounds the time sequence right away.

Yes: it shows two related but slightly different ideas.

A document can be described as:

• έγκυρο = valid
• ληγμένο = expired

In many real-life contexts, not expired is one reason something is valid, but Greek often uses both together for clarity, especially in administrative or official language.

So the sentence sounds natural in a bureaucratic context: the employee checked that the passport was both:

• valid
• not expired

That kind of explicit wording is very common in official Greek.