Learn Hardcore Croatian: Ona želi još jednom pogledati isti film. - She wants to watch the same movie once more.

Ona želi još jednom pogledati isti film. – fully explicit, often used for contrast (she wants to…, not someone else).
Želi još jednom pogledati isti film. – perfectly normal, usually what people say in context.

Without Ona, it could mean he/she/it wants…; the context tells you which.

What’s the difference between pogledati and gledati here?

The key difference is verbal aspect (perfective vs. imperfective).

gledati – imperfective: focuses on the process or duration (“to be watching”, “to watch in general”).
pogledati – perfective: focuses on a single, complete event (“to watch (once), to watch from beginning to end”).

With još jednom (“one more time”), you’re talking about repeating one whole viewing, so perfective pogledati is the most natural:

Ona želi još jednom pogledati isti film. – She wants to (re‑)watch the film one more time, as a complete event.

You could say još jednom gledati isti film, but that sounds more like “to (be) watch(ing) the same film once more” as an activity, and is less idiomatic here.

What exactly does još jednom mean, and how is it different from opet or ponovno?

još jednom literally means “one more time / once more”. It strongly suggests adding one more occurrence.

još jednom – “one more time, once more”
opet – “again”, neutral, very common in speech
ponovno – “again, anew”, a bit more formal or neutral‑written

In this sentence:

Ona želi još jednom pogledati isti film. – She wants to watch the same film one more time (emphasis on one additional viewing).
Ona želi opet pogledati isti film. – She wants to watch the same film again (repetition in general).
Ona želi ponovno pogledati isti film. – Similar to opet, a bit more neutral/formal.

All three are possible; još jednom makes the “one more time” idea the clearest.

Can I move još jednom to another place, like Ona želi pogledati isti film još jednom? Does that change the meaning?

Yes, you can move it, and the basic meaning stays the same.

All of these are grammatical and natural:

Ona želi još jednom pogledati isti film.
Ona želi pogledati isti film još jednom.

Word order in Croatian is relatively flexible. Moving još jednom mainly changes rhythm and slight emphasis, not the core meaning. In both examples, it still modifies the act of watching the film one more time.

Why is it isti film and not something like istog filma?

Because isti film is the direct object of pogledati, and direct objects are normally in the accusative case.

film is a masculine inanimate noun.
For masculine inanimate nouns, nominative singular = accusative singular.
- Nominative: film
- Accusative: film

The adjective isti must agree with film in gender, number, and case:

masculine, singular, accusative → isti film

istog filma is genitive singular (“of the same film”), used in phrases like:

naslov istog filma – the title of the same film

Is isti just a normal adjective? How would it change with other nouns?

Yes, isti behaves like an adjective (more exactly, a pronominal adjective) and agrees with the noun in gender, number, and case.

Some basic nominative singular forms:

masculine: isti film – the same film
feminine: ista knjiga – the same book
neuter: isto pivo – the same beer

In this sentence, isti film is accusative singular masculine, which happens to look identical to nominative: isti film.

Why is film not changing form at all? How do I know it’s the object?

For masculine inanimate nouns like film, the nominative and accusative singular forms are identical:

Nominative: film
Accusative: film

You know it’s the object because:

pogledati requires a direct object (what is watched? → the film),
film comes after the verb (and its adverbs/adverbials) in a typical SVO order,
there is already a clear subject (Ona).

So in Ona želi još jednom pogledati isti film, isti film is the direct object even though its form matches the nominative.

Can I use htjeti instead of željeti, like Ona hoće još jednom pogledati isti film?

Yes, that’s grammatically possible, but the nuance and style change slightly.

željeti (here: želi) – “to want, to desire”, a bit more neutral or polite.
htjeti (here: hoće) – “to want”, but in everyday speech can sound more direct, sometimes stronger (“she insists / she will (do it)”).

Examples:

Ona želi još jednom pogledati isti film. – She wants/would like to watch the same film one more time. (neutral)
Ona hoće još jednom pogledati isti film. – She wants to watch the same film one more time. (more colloquial/direct; depending on tone, can sound a bit more insistent)

Both are correct; želi is usually the safer, more neutral choice in standard language.

Could I say Ona želi da još jednom pogleda isti film instead of using the infinitive?

People do say that in everyday speech, and it will be understood, but in standard Croatian, after željeti the infinitive is preferred:

more standard: Ona želi još jednom pogledati isti film.
colloquial / regional (influenced by Serbian/Bosnian usage): Ona želi da još jednom pogleda isti film.

Meaning‑wise there is practically no difference here: both express her wish to watch the same film one more time. If you’re aiming at textbook/standard Croatian, use the infinitive construction.

How would I say “She wants to watch it once more” (without repeating the word film)? Where does the pronoun go?

You would normally use the clitic pronoun ga (“it” for a masculine singular object like film):

Ona ga želi još jednom pogledati.
(Without pronoun: Ona želi još jednom pogledati isti film.)

Key points:

ga is a clitic; it usually goes in the second position in the clause.
In Ona ga želi još jednom pogledati, the first word is Ona, so ga comes right after it.