Learn Hardcore Croatian: Njena prijateljica više voli odbojku i trenira je svaki utorak u istoj dvorani. - Her friend prefers volleyball and practices it every Tuesday in the same hall.

In everyday speech prijateljica usually means female friend, not necessarily a romantic partner. For “girlfriend” (romantic), people more often say djevojka (literally girl but commonly girlfriend), or they clarify by context.

So Njena prijateljica most naturally means her (female) friend.

Why is it njena prijateljica and not njen prijateljica or something else?

The possessive adjective has to agree with the noun in gender, number, and case.

The base possessive is njen / njezin = her
Feminine singular nominative form (for prijateljica) is njena / njezina

So:

njena prijateljica = her (female) friend
njezina prijateljica = same meaning, slightly more formal/standard
njen prijatelj = her (male) friend

You cannot say njen prijateljica because njen is the masculine (and neuter) form; it does not agree with the feminine noun prijateljica.

Could I use svoja instead of njena here, like Svoja prijateljica?

No, not in this sentence.

Svoj is a reflexive possessive and normally refers back to the grammatical subject of the clause, for example:

Ona voli svoju prijateljicu. = She loves her (own) friend.

But in your sentence, Njena prijateljica is itself the subject. You are introducing the subject, not referring back to an already established subject. Reflexive svoj is not normally used there.

So Njena prijateljica is correct; Svoja prijateljica is not.

Why is it više voli odbojku and not just voli odbojku? What does više add?

Voli odbojku = she likes volleyball.
Više voli odbojku = she likes volleyball more → she prefers volleyball.

Više is “more” and makes voli comparative. It can mean:

she likes volleyball more than some other sport (often understood from context), or
she likes volleyball more (in general), with emphasis on intensity or preference.

So više voli odbojku is usually best translated as prefers volleyball.

Why is odbojku used instead of odbojka?

The verb voljeti (to like/love) takes its object in the accusative case.

Dictionary form: odbojka (nominative, “volleyball”)
Accusative singular feminine: odbojku

Since odbojka is the thing she likes, it becomes the direct object and changes to odbojku:

Voli odbojku. = She likes volleyball.

What exactly is je in trenira je, and why is it in that position?

Je is the unstressed (clitic) form of the 3rd person feminine singular object pronoun = her / it.

Here it stands for odbojku (volleyball):

trenira odbojku → trenira je = she trains/practises it

About word order: Croatian clitic pronouns like je usually go very early in the clause, often right after the first stressed word:

Trenira je svaki utorak.
Svaki utorak je trenira.

You cannot put it at the very end (trenira svaki utorak je) and in neutral word order you don’t usually put it before the main verb in such a simple sentence.

Could je in trenira je refer to prijateljica instead of odbojku?

In theory, grammatically, je could refer to any feminine singular noun, including prijateljica. But here the meaning and the verb make it clear:

trenirati odbojku (to train/practise volleyball) is very natural
trenirati prijateljicu (to train one’s female friend) is possible, but unusual in everyday small‑talk

Because odbojku is the obvious thing you train as a sport, speakers automatically interpret je as referring back to odbojku, not to prijateljica. Context disambiguates it.

Can I just say … i trenira svaki utorak … and leave out je?

Yes, you can, but the meaning becomes slightly less specific.

… i trenira je svaki utorak … = and she trains/practises it every Tuesday (clearly referring back to volleyball).
… i trenira svaki utorak … = and she trains every Tuesday (it’s understood from context that this is volleyball, but it is not said explicitly).

Both are acceptable; including je simply makes the reference to volleyball explicit.

What tense/aspect is trenira, and why is it used for a repeated action?

Trenira is present tense of the imperfective verb trenirati (to train, to practise).

In Croatian, the present of an imperfective verb is the normal way to talk about:

habits and repeated actions:
- Trenira je svaki utorak. = She trains it every Tuesday.
general truths and ongoing activities

So using trenira in the present perfectly fits the idea of a regular weekly practice.

Why is it svaki utorak and not svakog utorka? Are both possible?

Both svaki utorak and svakog utorka are used, and both can mean every Tuesday.

Grammar:

svaki utorak – accusative masculine singular (used as a time expression: “(on) every Tuesday”)
svakog utorka – genitive masculine singular (also common in time expressions for habitual actions)

In everyday speech, svaki utorak is very common and perfectly correct. Svakog utorka sounds slightly more formal or literary, but the difference is small and mostly stylistic.

Why is it u istoj dvorani and not u istu dvoranu? What’s the case difference?

The preposition u can take either accusative or locative, depending on meaning:

u
- accusative → movement into something
u
- locative → location in something

Here we’re talking about where she trains (location), not where she is going, so we use locative:

u istoj dvorani = in the same hall/gym (locative: istoj dvorani)

Compare:

Idem u istu dvoranu. = I’m going into the same hall. (accusative: istu dvoranu)
Treniram u istoj dvorani. = I train in the same hall. (locative: istoj dvorani)

What does dvorana mean exactly? Is it specifically a sports hall?

Dvorana is a general word for a large hall. The exact meaning depends on context:

sportska dvorana = sports hall / gym
koncertna dvorana = concert hall
svećana dvorana = ceremonial hall

In your sentence, because we’re talking about volleyball practice, dvorana is naturally understood as a sports hall or gym. So u istoj dvorani here is best translated as in the same gym / sports hall.

Could the word order in the first part change, like Više voli odbojku njena prijateljica?

Yes, Croatian allows flexible word order, but word order affects emphasis and naturalness.

Neutral: Njena prijateljica više voli odbojku.
- Subject (Njena prijateljica) first, then what she does.
Više voli odbojku njena prijateljica.
- Puts strong emphasis on više voli odbojku (the liking) and leaves njena prijateljica to the end; this sounds marked or stylistic, not neutral everyday order.

For normal, neutral speech, the original order (Njena prijateljica više voli odbojku…) is the most natural.