Learn Hardcore Croatian: Na festivalu filmova redatelj govori o svojoj omiljenoj ulozi glumca. - At the film festival the director talks about his favorite role as an actor.

Yes. Croatian word order is fairly flexible. The original order is neutral and sets the scene first (at the festival), then tells you what the director is doing.

You could also say, for example:

Redatelj na festivalu filmova govori o svojoj omiljenoj ulozi glumca.
– slightly more emphasis on redatelj (the director).
Redatelj govori na festivalu filmova o svojoj omiljenoj ulozi glumca.

What you cannot do is separate prepositions from their nouns, e.g. you must keep na festivalu together, and o svojoj omiljenoj ulozi together. But moving those phrases around the verb and subject is usually fine and changes emphasis more than meaning.

Why is it na festivalu, not u festivalu?

Croatian usually uses:

na
- locative for events and public activities:
  na festivalu, na koncertu, na sastanku
  (at a festival, at a concert, at a meeting)
u
- locative for enclosed physical spaces:
  u kući, u kino-dvorani, u uredu
  (in the house, in the cinema hall, in the office)

So na festivalu corresponds to English at the festival.
u festivalu would sound like you are physically inside the festival as if it were a container, so it is not idiomatic here.

What does festivalu filmova literally mean, and why is filmova in that form?

Literally, festivalu filmova means “festival of films”.

festivalu – locative singular of festival (base form festival) because it follows na (location: at the festival).
filmova – genitive plural of film (base form film, nominative plural filmovi, genitive plural filmova).

The genitive often expresses possession or “of”-relations between two nouns:

festival filmova – a festival of films
časa engleskog – a lesson of English (English lesson)
muzej umjetnosti – a museum of art

You could also say na filmskom festivalu (“at the film festival”), using the adjective filmski instead of the genitive filmova. Both are correct; festival filmova sounds a bit more like “a festival whose content is films” and filmski festival like the set phrase “film festival”, but in practice they’re very close.

Which grammatical cases appear in this sentence, and what causes them?

The main cases here are:

redatelj – nominative singular (subject of the sentence)
na festivalu – festivalu is locative singular after na (location: at the festival)
filmova – genitive plural, specifying the type of festival (festival of films)
govori o – o always takes the locative case
svojoj omiljenoj ulozi – ulozi is locative singular (because of o), and svojoj omiljenoj are adjectives agreeing with ulozi in case, gender, and number
glumca – genitive singular, linked to ulozi: “role of an actor”

So the prepositions drive the cases:

na (here: static location) → locative
o (“about”) → locative

and the genitives filmova and glumca express “of X” relationships.

Why do we say govori o and not just govori? Is govoriti o a fixed pattern?

Yes, govoriti o + locative is a standard pattern meaning “to speak / talk about something”.

govoriti o filmu – to talk about a film
govoriti o politici – to talk about politics
govoriti o svojoj omiljenoj ulozi glumca – to talk about his favourite role as an actor

Without o, govoriti is more general:

govoriti hrvatski – to speak Croatian (here it takes a direct object in the accusative)
govoriti govor – to deliver a speech

You could also use pričati o + locative, which is a bit more informal and storytelling-like:

priča o svojoj omiljenoj ulozi glumca – he’s telling (talking) about his favourite role as an actor.

Why is it svojoj and not njegovoj for “his” in this sentence?

Croatian has a special reflexive possessive svoj that you use when the owner is the subject of the same clause.

Here, the subject is redatelj, and it’s his own favourite role, so we use svojoj:

redatelj govori o svojoj omiljenoj ulozi
– the director talks about his own favourite role.

If you said:

redatelj govori o njegovoj omiljenoj ulozi,

it usually implies that the favourite role belongs to some other male person, not the director himself (for example, “the director talks about his [= the actor’s] favourite role”).

Formally:

Base form: svoj
svojoj here is dative/locative feminine singular, agreeing with ulozi (also dat/loc feminine singular).

What exactly is omiljenoj grammatically, and why does it end in -oj?

Omiljenoj is an adjective meaning “favourite”, and here it is:

gender: feminine
number: singular
case: dative / locative

It agrees with ulozi, which is also feminine singular in the locative.

Base forms in nominative:

masculine: omiljeni
feminine: omiljena
neuter: omiljeno

In dative/locative feminine singular, it becomes omiljenoj:

o omiljenoj ulozi – about the favourite role
pričam o omiljenoj knjizi – I’m talking about my favourite book

So the -oj ending marks feminine singular dative/locative for adjectives.

Why is it ulozi glumca and not uloga glumca or ulogu glumca?

The preposition o requires the locative case, so the noun uloga must be in the locative:

nominative: uloga
accusative: ulogu
dative/locative: ulozi

Because we have o (“about”), we need o ulozi, not o uloga or o ulogu.

Then glumca is genitive singular of glumac, giving you a noun–noun relationship:

ulozi glumca – the role of an actor / an actor’s role

So the whole phrase:

o svojoj omiljenoj ulozi glumca
= about his favourite role of an actor / role as an actor.

Does glumca mean a specific actor, or can it be general like “as an actor”?

By itself, glumca in ulozi glumca can be:

specific: “the role of the actor” (if context already tells you which actor), or
generic: “his role as an actor” (actor in general, his acting role).

Croatian often uses singular nouns in a generic sense:

život psa – the life of a dog / dog’s life (in general)
uloga glumca – the role of an actor (either a particular actor or the role-type)

If you wanted to clearly indicate a specific actor, you would usually add a determiner:

uloga tog glumca – the role of that actor
uloga poznatog glumca – the role of a famous actor

What tense and aspect is govori? How would I say “was talking” or “talked”?

Govori is:

present tense
3rd person singular
of the imperfective verb govoriti.

It covers both English “he talks” and “he is talking”; Croatian does not have a separate progressive form.

To say “he talked / he was talking”, you use the past tense (perfect):

redatelj je govorio – he talked / he was talking
redatelj je govorio o svojoj omiljenoj ulozi glumca – the director was talking / talked about his favourite role as an actor.

Context usually tells you whether English should use simple past or past continuous.

What is redatelj exactly (gender, form), and is there a feminine form?

Redatelj is a masculine noun meaning “director (film, theatre)”.

nominative singular: redatelj
nominative plural: redatelji

The common feminine form is:

redateljica – female director
nominative plural: redateljice

In some other South Slavic varieties, you may also see režiser / režiserka, but in standard Croatian redatelj / redateljica is preferred, especially for film and theatre directors.

How do you pronounce redatelj, especially the lj at the end?

Redatelj is pronounced roughly:

re-da-telj, with stress usually on re: RÉ-da-telj.

The lj represents a single sound /ʎ/, a palatal “l”, similar to the lli in English million or Italian gl in famiglia.

So:

lj is one consonant in Croatian (like nj, dž), even though it’s written with two letters.
You do not pronounce it as separate l
- j; it’s one blended sound.