Αν χρειαστείς διευκρίνιση για το νέο πρόγραμμα, στείλε μου μήνυμα πριν από τη σύσκεψη.

After αν in a real future condition, Greek normally does not use θα.

So:

Αν χρειαστείς... = If you need... / If you happen to need...

This form is the normal Greek way to express a possible future situation after if. In grammar books, χρειαστείς is often described as an aorist subjunctive or perfective non-past form.

By contrast, αν θα χρειαστείς is not the standard pattern here.

It comes from the verb χρειάζομαι, which means to need.

The form χρειαστείς is a different stem and form of the same verb:

• dictionary form: χρειάζομαι
• present 2nd person singular: χρειάζεσαι = you need / you are needing
• form used here: χρειαστείς = you need in a future/conditional sense

So Greek changes the shape of the verb depending on aspect and sentence type. Here, the sentence is talking about a possible one-time future need, so Greek uses χρειαστείς, not the present form χρειάζεσαι.

Because the sentence is about a single possible future situation, not an ongoing state.

• αν χρειαστείς διευκρίνιση = if you end up needing clarification
• αν χρειάζεσαι διευκρίνιση = more like if you need clarification in a general or ongoing sense

Both can be possible in the right context, but χρειαστείς fits better when the speaker means:

If at some point you need clarification, send me a message.

That is why the perfective form is used.

It is addressing one person, in the informal singular.

You can tell from:

• χρειαστείς
• στείλε

Both are singular forms.

If you wanted to say the same thing to more than one person or in a formal singular way, you would say:

Αν χρειαστείτε διευκρίνιση για το νέο πρόγραμμα, στείλτε μου μήνυμα πριν από τη σύσκεψη.

So:

• χρειαστείς / στείλε = singular informal
• χρειαστείτε / στείλτε = plural or formal

Στείλε is the aorist imperative of στέλνω and is used for one complete action:

στείλε μου μήνυμα = send me a message

This fits the idea of a single action: one message, one time.

By contrast, στέλνε is the present imperative, which usually suggests repeated, ongoing, or habitual action, something more like:

• keep sending
• send regularly

So στείλε is the natural choice here.

Μου means to me.

In Greek, weak object pronouns like μου, σου, του, της often come before the verb in ordinary statements:

• Μου στέλνεις μήνυμα. = You send me a message.

But with an affirmative imperative, they usually come after the verb:

• Στείλε μου μήνυμα. = Send me a message.

So the word order here is normal Greek imperative word order.

Greek often leaves out the article when the noun is indefinite or used in a general sense.

So:

• χρειαστείς διευκρίνιση = need clarification / some clarification
• στείλε μου μήνυμα = send me a message / message me

If the speaker wanted to make the noun more explicitly a message or a clarification, they could say:

• μια διευκρίνιση
• ένα μήνυμα

But the article-less version sounds very natural here.

Here για means about / regarding.

So:

διευκρίνιση για το νέο πρόγραμμα = clarification about the new program

The noun πρόγραμμα is broad in Greek and can mean things like:

• program
• schedule
• timetable
• plan

The exact meaning depends on context. So if the English translation says program, that is fine, but in another context schedule or plan might also be natural.

Yes. Both are possible.

Πριν από + noun is a very common and standard way to say before:

• πριν από τη σύσκεψη = before the meeting

In everyday Greek, people also very often say:

• πριν τη σύσκεψη

So από is often optional here, especially in speech.

Both versions are natural, but πριν από τη σύσκεψη can sound a little fuller or slightly more formal.

The full feminine accusative singular article is την, but the final -ν is often dropped before many consonants.

Since σύσκεψη begins with σ, Greek normally writes:

τη σύσκεψη

You keep the -ν more often before vowels and certain consonants, for example:

• την αίθουσα
• την πόρτα

So τη σύσκεψη is the expected form here.