Η δασκάλα μάς είπε ότι το σεμινάριο πρόκειται να είναι πιο δύσκολο από το προηγούμενο.

Μας / μάς and εμάς are all forms of “us”, but they behave differently.

• μας (without accent) is the weak / clitic form:

  • as object pronoun:
    
    • Η δασκάλα μας είπε. = The teacher told us.
  • as possessive (our):
    
    • Η δασκάλα μας. = Our teacher.

• μάς (with accent) is used mainly:

  • for emphasis:
    
    • Η δασκάλα μάς είπε, όχι τους άλλους.
      = The teacher told *us, not the others.*
  • or to avoid ambiguity with the possessive μας in writing.

• εμάς is the strong/stressed form of “us”:

  • often used for contrast or alone:
    
    • Εμάς μάς είπε την αλήθεια. = She told *us the truth.*
    • Ποιον φώναξε; – Εμάς. = Whom did she call? – Us.

In your sentence, μάς is written with an accent to show it is a stressed object pronoun (told us) and not the possessive (our). In everyday writing you will also often see μας είπε without the accent, unless the writer wants special emphasis or clarity.

In Modern Greek, weak object pronouns like με, σε, τον, την, το, μας, σας, τους are clitics. In normal statements (indicative, not imperative), they usually go before the main verb:

• Μάς είπε. = She told us.
• Τον είδα. = I saw him.
• Σας κάλεσα. = I called you (plural).

So Η δασκάλα μάς είπε is the standard order.

Putting the clitic after the verb (είπε μάς) is generally wrong in this context. Pronouns go after the verb mainly in:

• positive imperatives:
  
  • Πες μας. = Tell us.
  • Δώσε μου το βιβλίο. = Give me the book.
• some fixed expressions and older / more literary styles.

So in your sentence, μάς είπε (or μας είπε) is the correct order; είπε μάς would sound ungrammatical in modern everyday Greek.

Both come from λέω (to say, to tell), but they are different tenses/aspects:

• είπε = aorist (simple past)

  • a single, completed act of speaking:
    
    • Η δασκάλα μάς είπε… = The teacher told us (once)…

• έλεγε = imperfect (past continuous / habitual)

  • repeated or ongoing action in the past:
    
    • Η δασκάλα μάς έλεγε συνέχεια ότι…
      = The teacher kept telling us / was always saying that…

In your sentence, it’s about one specific moment when she informed you about the seminar, so είπε (aorist) is the correct and natural choice.

Here, ότι is a conjunction meaning “that” in indirect speech:

• Η δασκάλα μάς είπε ότι το σεμινάριο…
  = The teacher told us that the seminar…

You can usually replace ότι with πως in this meaning:

• Η δασκάλα μάς είπε πως το σεμινάριο πρόκειται να είναι…

Both are correct. Ότι is often felt as a bit more neutral/formal, and πως as a bit more colloquial, but in practice they are very often interchangeable.

Be careful with ό,τι (with comma or accent), which is not the same word:

• ό,τι = “whatever / anything that” (relative / indefinite pronoun)
  
  • Φάε ό,τι θέλεις. = Eat whatever you want.

So:

• ότι (no comma, no extra accent) = that (introduces a clause).
• ό,τι (comma or accent) = whatever / anything that.

Both refer to the future:

• θα είναι = “will be / is going to be” (neutral future):

  • Το σεμινάριο θα είναι δύσκολο. = The seminar will be difficult.

• πρόκειται να είναι literally comes from πρόκειται (it is intended/it is expected), and with να + verb it often means:

  • something planned, scheduled or expected, or
  • something about to happen / going to happen.

In your sentence:

• Το σεμινάριο πρόκειται να είναι πιο δύσκολο…
  suggests more the idea of an already-arranged future fact, something on the schedule or officially decided.

In many everyday situations, πρόκειται να είναι and θα είναι overlap, and you could say:

• Η δασκάλα μάς είπε ότι το σεμινάριο θα είναι πιο δύσκολο…

with very similar meaning. Πρόκειται να just sounds a bit more formal / “scheduled”.

Adjectives in Greek agree in gender, number, and case with the noun they describe.

• το σεμινάριο is:
  • neuter, singular, nominative.

So the adjective δύσκολος must also be:

• δύσκολο (neuter singular nominative):

το σεμινάριο – πιο δύσκολο

If it were a feminine noun, e.g. η άσκηση (the exercise):

• Η άσκηση είναι πιο δύσκολη.

Or a masculine noun, e.g. ο διαγωνισμός (the exam):

• Ο διαγωνισμός είναι πιο δύσκολος.

Here, σεμινάριο is neuter, so πιο δύσκολο is the only correct form.

Yes. Greek has two ways to form the comparative:

1. Analytic: πιο + adjective

   • πιο δύσκολο = more difficult

2. Synthetic: adjective + -τερος/-τερη/-τερο

   • δυσκολότερο = more difficult

Both:

• πιο δύσκολο από το προηγούμενο
• δυσκολότερο από το προηγούμενο

are grammatically correct and mean the same thing.

In modern spoken Greek, πιο δύσκολο is more common and neutral.
δυσκολότερο sounds more formal, careful, or written.

In comparisons, Greek usually uses:

• πιο + adjective + από
  
  • πιο δύσκολο από το προηγούμενο
    = more difficult than the previous (one).

Από is the standard preposition for comparisons and is always correct here.

You sometimes see παρά in comparisons, especially:

• after comparative adverbs or negatives, and often when what follows is a phrase or clause rather than a plain noun:
  • Καλύτερα να φύγουμε παρά να περιμένουμε.
  • Πιο πολύ το έχω για χόμπι παρά για δουλειά.

With a straightforward noun like το προηγούμενο, από is the natural choice.
πιο δύσκολο παρά το προηγούμενο would sound odd here; από is the correct preposition.

Greek often omits a repeated noun when it is clear from the context. This is very similar to English:

• English: …more difficult than the previous one (we drop seminar).
• Greek: πιο δύσκολο από το προηγούμενο (σεμινάριο).

The full form would be:

• πιο δύσκολο από το προηγούμενο σεμινάριο.

But since σεμινάριο has just been mentioned, it is understood, so only το προηγούμενο is said. This kind of ellipsis is natural and very common in Greek.

Greek nouns have grammatical gender. δασκάλα is the feminine form of “teacher”:

• η δασκάλα = the (female) teacher
• ο δάσκαλος = the (male) teacher

So:

• Η δασκάλα μάς είπε… = The (female) teacher told us…
• Ο δάσκαλος μάς είπε… = The (male) teacher told us…

Only the article and the noun change. The rest of the sentence stays the same:

• Ο δάσκαλος μάς είπε ότι το σεμινάριο πρόκειται να είναι πιο δύσκολο από το προηγούμενο.

Σεμινάριο is a neuter noun borrowed from international vocabulary (seminar). Its basic forms:

• το σεμινάριο – the seminar (singular, nominative/accusative)
• του σεμιναρίου – of the seminar (singular, genitive)
• τα σεμινάρια – the seminars (plural, nominative/accusative)
• των σεμιναρίων – of the seminars (plural, genitive)

Like most neuter nouns in -ιο, it keeps -ιο in the singular and becomes -ια in the plural.

Because it’s neuter, any adjectives referring to it (like δύσκολος) must appear in the neuter form (δύσκολο, πιο δύσκολο, δυσκολότερο, etc.), as in your sentence.