Režisér mluví o filmu.

Because the preposition o normally requires the locative case when it means about.

• basic noun: film
• after o: o filmu

So Režisér mluví o filmu uses:

• režisér = nominative, because it is the subject
• o filmu = locative, because it follows o

This is a very common Czech pattern:

• mluvit o něčem = to speak about something
• číst o něčem = to read about something
• přemýšlet o něčem = to think about something

Mluví is the 3rd person singular present tense of the verb mluvit.

So:

• mluvit = infinitive, to speak
• mluví = he/she/it speaks or is speaking

Because režisér is singular, the verb is also singular:

• Režisér mluví = The director speaks / is speaking

In Czech, present tense often covers both the simple present and the present continuous idea that English separates.

Czech does not have articles like the and a/an.

So a Czech sentence such as Režisér mluví o filmu could correspond to English as:

• The director is talking about the film
• A director is talking about a film
• The director talks about the film

The exact English article depends on context, not on a separate Czech word.

Režisér is in the nominative case, because it is the subject of the sentence.

In this sentence:

• Režisér = the person doing the action
• mluví = the action
• o filmu = what he is speaking about

So the basic structure is:

• subject
  • verb
    • prepositional phrase

Yes, režisér is a masculine animate noun.

That matters because Czech nouns belong to gender classes, and gender affects:

• case endings
• adjective agreement
• past tense forms
• some numeral forms

Here, the gender does not change the form of mluví, because present tense verbs do not show gender. But gender would matter in other contexts, for example in the past tense:

• Režisér mluvil. = The director spoke.
• Režisérka mluvila. = The female director spoke.

So yes, it matters, even if you do not see much of it in this specific sentence.

Yes. Czech word order is fairly flexible because case endings show grammatical roles.

The neutral order here is:

• Režisér mluví o filmu.

But other orders are possible, for example:

• O filmu mluví režisér.
• Mluví o filmu režisér.

These alternatives can sound more marked and may shift the emphasis:

• Režisér mluví o filmu. = neutral statement
• O filmu mluví režisér. = emphasis on about the film
• Mluví o filmu režisér. = can sound like contrast or a question-like emphasis depending on context

So Czech word order is not random, but it is more flexible than English.

The hardest part for many English speakers is ř, which is a special Czech sound.

A rough pronunciation guide:

• Režisér ≈ rzheh-zhee-sair
• mluví ≈ mloo-vee
• o filmu ≈ o fee-lmoo

About ř:

• it is not exactly an English sound
• it is somewhat like a rolled or trilled r mixed with a zh sound, like the s in measure

Many learners first approximate it with rzh, which is fine as a temporary step.

Also note:

• ž sounds like the s in measure
• í is a long ee sound
• Czech stress is usually on the first syllable of the word

So the stress is roughly:

• RE-ži-sér
• MLU-ví
• O FIL-mu

The accent mark in í shows that the vowel is long.

So:

• i = short vowel
• í = long vowel

In mluví, the final vowel is pronounced longer: mloo-VEE

In Czech, vowel length is important because it can distinguish words, so it is not just a spelling detail.

It can mean either, depending on context.

Czech present tense often covers both:

• speaks in a general or habitual sense
• is speaking in a right-now sense

So Režisér mluví o filmu could mean:

• The director speaks about the film
• The director is talking about the film

Context tells you which one is meant.

Not always, but in this sentence that is the natural meaning.

With the locative case, o often means:

• about
• concerning
• sometimes on in certain contexts

Examples:

• mluvit o filmu = to talk about a film
• kniha o historii = a book about history

So here o filmu clearly means about the film.

Yes. Hovořit is another verb meaning to speak.

So:

• Režisér mluví o filmu.
• Režisér hovoří o filmu.

Both are correct, but they differ a little in style:

• mluvit = more common, everyday
• hovořit = a bit more formal or literary

A learner will hear mluvit much more often in ordinary conversation.

The dictionary form is film.

When you look nouns up in a dictionary, you usually find the nominative singular form. Here:

• dictionary form: film
• form in the sentence: filmu

That change happens because of case:

• film = nominative
• o filmu = locative after o

So when learning vocabulary, it is useful to memorize both the base form and common case patterns.