Na tržnici sam kupila dva suncokreta za blagovaonicu.

Kupila shows that the speaker is female.

In Croatian past tense, the main verb agrees with the subject in gender and number:

• ja sam kupila = I bought (female speaker)
• ja sam kupio = I bought (male speaker)

So this sentence was said by a woman.

Sam is the auxiliary verb used to form the past tense.

Croatian past tense is often built like this:

• sam
  • past participle

So:

• sam kupila = I bought

More fully, the sentence could be understood as:

• Ja sam kupila = I bought

But Croatian often leaves out ja because the verb form already makes the subject clear.

Croatian usually does not need subject pronouns when the verb already shows who is doing the action.

So instead of saying:

• Ja sam kupila...

it is very natural to say:

• Sam kupila...
• or, as here, Na tržnici sam kupila...

The I is understood from sam and kupila.

This is mainly because sam is a clitic, and Croatian clitics usually go in the second position in the sentence or clause.

So if the sentence begins with Na tržnici, then sam naturally comes right after it:

• Na tržnici sam kupila...

This word order is very normal in Croatian.

You may also see:

• Kupila sam dva suncokreta na tržnici.

That is also correct, but the emphasis is a bit different. The original sentence puts early focus on where the action happened.

With tržnica (market), Croatian normally uses na, not u, when talking about being at the market:

• na tržnici = at the market

This is just the usual idiomatic choice.

Also, after na in this meaning of location, Croatian uses the locative case:

• tržnica → tržnici

So:

• na tržnici = at the market

Tržnici is locative singular.

The basic form is:

• tržnica = market

After na when it means in/on/at a place, Croatian often uses the locative:

• na tržnici = at the market

So the ending changes because the noun is not in its dictionary form anymore.

After the numbers 2, 3, and 4, Croatian uses a special pattern.

With masculine nouns like suncokret, you get:

• dva suncokreta = two sunflowers

not:

• dva suncokreti

The noun after dva looks like the genitive singular form:

• suncokret = sunflower
• suncokreta = of a sunflower / after dva

This is one of the number patterns learners need to get used to.

Because suncokret is a masculine noun.

Croatian has different forms of two depending on gender:

• dva for masculine and neuter
• dvije for feminine

So:

• dva suncokreta = two sunflowers (masculine noun: suncokret)
• dvije ruže = two roses (feminine noun: ruža)

After dva, the noun is in the form traditionally described as genitive singular for this kind of masculine noun.

So:

• suncokret = nominative singular
• suncokreta = form used after dva

That is why the sentence says:

• dva suncokreta

This is a very common Croatian number construction.

Za here means for, and it takes the accusative case.

The basic noun is:

• blagovaonica = dining room

In the accusative singular, it becomes:

• blagovaonicu

So:

• za blagovaonicu = for the dining room

This means the sunflowers were bought for use in that room, probably as decoration.

It is accusative singular.

The noun is:

• blagovaonica = dining room

After the preposition za meaning for, Croatian uses the accusative:

• za blagovaonicu

This is why the ending changes from -a to -u.

In general, za + accusative can have different meanings in Croatian depending on context, but here it clearly means for the dining room, not motion toward it.

So in this sentence it means the sunflowers were intended for that room.

A learner should understand it as:

• bought for the dining room
• not to/into the dining room

Yes, but that would change the meaning.

• kupila = perfective, a completed action: I bought
• kupovala = imperfective, ongoing/repeated/background action: I was buying / I used to buy

So the original kupila tells us this was one completed purchase.

Grammatically, suncokret means sunflower, but in real life the exact interpretation depends on context.

In this sentence, because of za blagovaonicu, many learners would naturally imagine actual flowers bought for decoration. But without more context, it could in principle refer to decorative sunflowers too.

The grammar itself does not force one interpretation beyond two sunflowers.

Usually at the market is the most natural translation here.

English sometimes allows both depending on context, but Croatian na tržnici is the standard way to express being at the marketplace. So at the market is the safest and most natural choice.