Learn Hardcore Croatian: Navečer ponekad gledamo seriju na televiziji umjesto filma. - In the evening we sometimes watch a series on television instead of a movie.

Navečer – very common, means “in the evening / in the evenings” in a general, habitual sense.
- Navečer ponekad gledamo seriju. = In the evenings we sometimes watch a series.
Uvečer – also means “in the evening” but sounds a bit more formal or bookish, and is less frequent in everyday speech.
Večer alone usually means “evening” as a noun, not as an adverb of time:
- Večer je bila hladna. = The evening was cold.

So in your sentence, Navečer is the most natural and typical choice for “In the evening(s) / At night (in the evening time)”.

Where can I put ponekad in the sentence? Is Navečer ponekad gledamo… the only correct word order?

Croatian word order is flexible, especially with adverbs like ponekad (“sometimes”). All of these are possible and correct:

Navečer ponekad gledamo seriju na televiziji umjesto filma.
Ponekad navečer gledamo seriju na televiziji umjesto filma.
Gledamo ponekad navečer seriju na televiziji umjesto filma. (sounds less neutral, more marked/emphatic)

The most natural and neutral are the first two.

General rule: adverbs of frequency (ponekad, često, uvijek, nikad) typically go:

before the verb: ponekad gledamo, često gledamo, or
near the beginning with a time word: Navečer ponekad gledamo… / Ponekad navečer gledamo…

Why is it gledamo and not something like mi gledamo? Where did the pronoun “we” go?

In Croatian, the verb ending itself shows the person and number, so the subject pronoun is usually dropped:

gledamo = we watch
- gledam = I watch
- gledaju = they watch

So:

Gledamo seriju. = We are watching a series.

You can say Mi gledamo seriju, but that’s usually only when you want to emphasize the subject:

Mi gledamo seriju, a oni gledaju film.
= We watch a series, and they watch a film.

In normal, neutral sentences, you leave out mi.

Why is it seriju and not serija? What case is that?

Serija is a feminine noun (like žena, knjiga). Its singular forms are:

Nominative: serija (subject)
Accusative: seriju (direct object)

Here, seriju is the direct object of the verb gledamo (we watch what? → a series), so it must be in the accusative:

(Mi) gledamo seriju.

If it were the subject, you’d use nominative:

Serija je jako zanimljiva. = The series is very interesting.

So: seriju = accusative singular feminine.

The English translation is “a series / a TV show”. Why is there no word like “a”/“the” in Croatian?

Croatian has no articles (no direct equivalent of “a”, “an”, or “the”).

Definiteness and specificity are understood from context, word order, and sometimes from additional words (e.g. taj, ovaj, onaj = that/this).

So gledamo seriju can mean:

we watch a series
we watch the series
we watch our show (if context makes it clear which one)

You only specify if needed:

gledamo onu seriju = we watch that series
gledamo svoju omiljenu seriju = we watch our favorite series

Could I say gledamo serije if we often watch different series, not just one?

Yes.

gledamo seriju – one specific series / show (at a time, or a particular one you mean)
gledamo serije – series in general or more than one series

Compare:

Navečer ponekad gledamo seriju na televiziji umjesto filma.
= In the evening we sometimes watch a (specific) series instead of a movie.
Navečer ponekad gledamo serije na televiziji umjesto filmova.
= In the evenings we sometimes watch (various) series instead of movies.

Both are grammatically correct; it depends on what you want to say.

Why is it na televiziji and not na televiziju?

This is a location vs direction difference:

na televiziji → where something is happening (location)
- case: locative
- used with na + locative = on / at a place
- Gledamo seriju na televiziji. = We watch a series on TV.
na televiziju → to where something is moving (direction)
- case: accusative
- used with na + accusative = onto / to a place
- Stavili su film na televiziju. = They put the film on (to) TV (e.g., broadcast it).

In your sentence, you’re describing where you watch (on TV), so na televiziji (locative) is correct.

Why is it umjesto filma and not umjesto film? What case follows umjesto?

The preposition umjesto (“instead of”) always takes the genitive case.

Film is a masculine noun. Its singular forms are:

Nominative: film
Genitive: filma

So:

umjesto filma = instead of a/the film
umjesto čaja = instead of tea
umjesto brata = instead of (my) brother

That’s why you need filma, not film.

Is there any nuance to umjesto? Does it always mean “instead of”?

Yes, umjesto basically always means “instead of / in place of”.

It can be used:

With nouns:
- Pijem vodu umjesto soka. = I drink water instead of juice.
- Navečer gledamo seriju umjesto filma.
With verbs, in a clause:
- Umjesto da uči, on igra igrice. = Instead of studying, he plays games.

In your sentence it’s a very direct “X instead of Y”.

Would Navečer ponekad gledamo film umjesto serije also be correct?

Yes, that’s perfectly correct. You’ve just swapped which thing is preferred:

Navečer ponekad gledamo seriju na televiziji umjesto filma.
→ We sometimes watch a series instead of a film.
Navečer ponekad gledamo film na televiziji umjesto serije.
→ We sometimes watch a film instead of a series.

The structure and grammar stay the same; only the nouns change places.

Is gledamo here present simple or present continuous? Could it mean “we are watching” right now?

Croatian present tense covers both English present simple and present continuous, depending on context:

Habitual / repeated:
- Navečer ponekad gledamo seriju.
  → We sometimes watch a series in the evenings.
Right now (with context/time expressions):
- Sad gledamo seriju. = We are watching a series now.

In your sentence, because of Navečer and ponekad, it clearly describes a habit, not what you are doing at this exact moment.

Could I change the word order to Seriju ponekad navečer gledamo na televiziji umjesto filma?

Yes, that’s grammatically correct, but it sounds more emphatic and less neutral.

By moving seriju to the front, you emphasize what you watch:

Seriju ponekad navečer gledamo na televiziji umjesto filma.
~ It’s a series (rather than something else) that we sometimes watch in the evening on TV instead of a film.

Neutral, everyday style prefers:

Navečer ponekad gledamo seriju na televiziji umjesto filma.

Word order in Croatian is flexible, but shifting elements often adds some emphasis or focus.

Is there any difference between gledamo seriju na televiziji and gledamo seriju na TV-u?

Both are correct and common:

na televiziji – more neutral, slightly more formal; full word.
na TV-u – everyday speech, using the abbreviation TV with the Croatian case ending -u.

Examples:

Navečer ponekad gledamo seriju na televiziji.
Navečer ponekad gledamo seriju na TV-u.

Meaning is the same: “on TV”. The choice is mostly about style and context (spoken vs written, formal vs informal).