Ona ne zna odgovor, ali ima pitanje.

A natural breakdown is:

• Ona = she
• ne zna = does not know
• odgovor = answer / the answer
• ali = but
• ima = has
• pitanje = question / a question

So the structure is very close to English: She does not know the answer, but has a question.

Yes. Serbian often drops subject pronouns when the subject is clear from the verb form or from context.

So you could also say:

• Ne zna odgovor, ali ima pitanje.

That still means She doesn’t know the answer, but she has a question if the context already makes it clear who she is.

Using ona can add clarity, emphasis, or contrast. For example, it may suggest something like she doesn’t know it, even if someone else might.

Because in Serbian, the negative particle ne is usually written separately from the verb:

• ne znam = I don’t know
• ne znaš = you don’t know
• ne zna = he/she/it doesn’t know

So ne zna is the normal spelling.

A few common verbs are exceptions and have fused negative forms, such as:

• nemam = I don’t have
• nisam = I am not
• neću = I will not

But znati is not one of those exceptions.

Both are direct objects, so they are in the accusative case.

However, in this sentence their accusative forms happen to look the same as their dictionary forms:

• odgovor is a masculine inanimate noun, and masculine inanimate nouns usually have the same nominative and accusative singular form.
• pitanje is a neuter noun, and neuter singular nouns also usually have the same nominative and accusative form.

So:

• nominative: odgovor, pitanje
• accusative: odgovor, pitanje

That is why you do not see a visible ending change here.

Because Serbian does not have articles like English the and a/an.

So a noun like odgovor can mean:

• an answer
• the answer

and pitanje can mean:

• a question
• the question

The exact meaning depends on context.

In this sentence, English naturally uses the answer and a question, but Serbian expresses that without articles.

Yes, it is natural and common.

Serbian often uses imati + noun in situations where English also uses have:

• Imam pitanje. = I have a question.
• Ima problem. = He/She has a problem.
• Imamo ideju. = We have an idea.

Depending on context, Serbian could also use other expressions, such as:

• želi da postavi pitanje = wants to ask a question
• postavlja pitanje = is asking a question

But ima pitanje is perfectly normal.

Ali means but and connects two contrasting ideas:

• Ona ne zna odgovor = she doesn’t know the answer
• ali ima pitanje = but she has a question

So ali introduces contrast, just like English but.

It usually comes between the two clauses, as it does here.

Yes. Serbian word order is more flexible than English because case endings and verb forms carry a lot of grammatical information.

The sentence as written is a neutral, natural order:

• Ona ne zna odgovor, ali ima pitanje.

But other orders are possible for emphasis. For example:

• Ona ima pitanje, ali ne zna odgovor.
  Same basic meaning, but the first idea is now she has a question.

• Odgovor ne zna, ali ima pitanje.
  More marked, with extra emphasis on the answer.

So the original version is probably the best one for a learner to use first, but it is good to know that Serbian is not as rigid as English about word order.