Trenutno ne mogu razgovarati; na sastanku sam.

Because Croatian often leaves out subject pronouns when the verb form already makes the subject clear.

• mogu = I can
• sam = I am

So Trenutno ne mogu razgovarati; na sastanku sam. already clearly means I currently can’t talk; I’m in a meeting.

You could add ja for emphasis, but it is usually unnecessary:

• Ja trenutno ne mogu razgovarati. = I can’t talk right now.

Trenutno means currently, at the moment, or right now.

In this sentence it appears at the beginning:

• Trenutno ne mogu razgovarati.

That placement is very natural. But Croatian word order is flexible, so you may also hear:

• Ne mogu trenutno razgovarati.
• Ne mogu razgovarati trenutno.

The first version is the most neutral for a message like this.

Because the meaning is I can’t talk, not simply I am not talking.

• ne mogu razgovarati = I cannot talk / I’m unable to talk
• ne razgovaram = I am not talking / I’m not having a conversation

So if you are unavailable because of a meeting, ne mogu razgovarati is the better choice.

Grammar-wise:

• mogu is the present tense of moći = can, to be able to
• razgovarati is the infinitive = to talk / to converse

This modal verb + infinitive structure works much like English:

• Mogu doći. = I can come.
• Ne mogu čekati. = I can’t wait.

They are related, but not identical.

• razgovarati = to have a conversation, to talk with someone
• govoriti = to speak
• pričati = to talk / chat / tell stories, often more informal

In this sentence, razgovarati fits well because the idea is I can’t talk/converse right now.

Compare:

• Ne mogu razgovarati. = I can’t talk right now.
• Ne mogu govoriti. = I can’t speak.
  This can sound more literal, as if speaking itself is impossible.
• Ne mogu pričati. = I can’t talk.
  Very common and natural in everyday speech, a bit more casual.

Both can exist, but na sastanku sam is very natural because sam is a short clitic form of to be, and clitics in Croatian usually come in the second position of the clause.

Here, the first unit is na sastanku, so sam comes after it:

• Na sastanku sam.

You will also hear:

• Ja sam na sastanku.

That is also correct, because now ja is in first position and sam comes second.

So the main point is:

• sam usually does not stand completely freely
• it tends to appear in second position

Because the idiomatic Croatian expression is biti na sastanku = to be at/in a meeting.

So:

• na sastanku sam = I’m in a meeting

Even though English says in a meeting, Croatian uses na here. This is just something to learn as a fixed expression.

A useful contrast:

• Idem na sastanak. = I’m going to a meeting.
  (motion, so na
  • accusative)
• Na sastanku sam. = I’m at/in a meeting.
  (location, so na
  • locative)

Sastanku is in the locative singular.

The base noun is:

• sastanak = meeting

After the preposition na, when you are talking about location, Croatian uses the locative:

• na sastanku = at/in the meeting

So:

• sastanak → dictionary form
• na sastanku → locative singular

This is a very common pattern:

• na poslu = at work
• na fakultetu = at the university
• u uredu = in the office

No. It is correct, but not necessary.

The semicolon links two closely related statements:

• Trenutno ne mogu razgovarati; na sastanku sam.

You could also write:

• Trenutno ne mogu razgovarati. Na sastanku sam.
• Trenutno ne mogu razgovarati, na sastanku sam.
• Trenutno ne mogu razgovarati jer sam na sastanku.

All of these are natural. In text messages, people often use simpler punctuation:

• Ne mogu sad razgovarati, na sastanku sam.

It is neutral and very natural. You can use it in many situations: messages, calls, work chats, and everyday communication.

• Neutral: Trenutno ne mogu razgovarati; na sastanku sam.
• More casual: Ne mogu sad pričati, na sastanku sam.
• More formal/polite: Trenutno nisam u mogućnosti razgovarati; na sastanku sam.

For most real-life use, the original sentence is perfectly fine.

Yes.

• trenutno = currently / at the moment
• sad = now, right now
• sada = now, slightly more neutral or careful than sad

All of these work:

• Trenutno ne mogu razgovarati.
• Sad ne mogu razgovarati.
• Sada ne mogu razgovarati.

In everyday speech, sad is extremely common:

• Ne mogu sad pričati.

The original sentence is fine, but in casual everyday use, many speakers would shorten it a bit. Common versions include:

• Ne mogu sad razgovarati, na sastanku sam.
• Ne mogu sad pričati, na sastanku sam.
• Na sastanku sam, ne mogu razgovarati.
• Trenutno sam na sastanku. Ne mogu razgovarati.

So the sentence you were given is correct and natural, but casual speech often prefers sad and sometimes pričati instead of razgovarati.