Kod kuće sam stavila losos u frižider, a cvijeće u vazu.

Kod kuće means at home.

• kod often means at/near/by someone's place
• kuće is the genitive form of kuća (house/home)

As a fixed expression, kod kuće simply means at home.
It is very common in Croatian and does not literally need to be translated word-for-word.

Examples:

• Ostajem kod kuće. = I'm staying at home.
• Radim kod kuće. = I work from home / at home.

Both sam stavila and stavila sam are possible in Croatian, but word order follows some special rules.

In this sentence, sam is a clitic, a short unstressed form of to be used to make the past tense. Clitics usually go in the second position of the clause.

So in:

• Kod kuće sam stavila losos u frižider...

the phrase Kod kuće comes first, and then the clitic sam comes in second position.

You could also hear:

• Stavila sam losos u frižider...

That is also correct.

Stavila is the past tense form of staviti, which means to put.

The ending -la shows that the speaker is female.

Compare:

• Ja sam stavila = I put / I have put (female speaker)
• Ja sam stavio = I put / I have put (male speaker)

So this sentence tells us that the speaker is female.

Croatian often leaves out subject pronouns when they are not necessary.

So instead of saying:

• Ja sam stavila...

it is very natural to say:

• Sam stavila... or, more naturally in a full sentence, Kod kuće sam stavila...

The form sam stavila already tells you the subject is I, so ja is usually unnecessary unless you want emphasis.

Here losos is the direct object of the verb stavila. With staviti, the thing being put is in the accusative case.

For masculine inanimate nouns, the accusative is often the same as the nominative.

So:

• nominative: losos
• accusative: losos

That is why the form does not change.

Compare with a masculine animate noun:

• vidim psa = I see a dog Here the accusative changes because pas is animate.

Because u can take different cases depending on the meaning.

• u + accusative = movement into something
• u + locative = location in something

In this sentence, the idea is putting something into a place, so Croatian uses the accusative:

• u frižider = into the fridge
• u vazu = into the vase

Compare:

• Losos je u frižideru. = The salmon is in the fridge.
• Cvijeće je u vazi. = The flowers are in the vase.

So:

• stavila sam losos u frižider = movement into the fridge
• losos je u frižideru = location in the fridge

Because vaza is a feminine noun, and here it is after u expressing movement, so it goes into the accusative case.

For many feminine nouns ending in -a, the accusative singular ends in -u:

• vaza → vazu
• torba → torbu
• kuća → kuću

So:

• u vazu = into the vase

Cvijeće is the noun flowers (collective/mass-style noun in Croatian), and in this sentence it is the direct object.

Its nominative and accusative forms are the same here, so you see:

• cvijeće

This is normal for many neuter nouns.

Compare:

• nominative: cvijeće
• accusative: cvijeće

So:

• stavila sam cvijeće u vazu = I put the flowers into the vase

Croatian often omits repeated words when they are understood from context.

So:

• Kod kuće sam stavila losos u frižider, a cvijeće u vazu.

literally has the sense:

• At home, I put the salmon in the fridge, and the flowers in the vase.

The full version would be:

• Kod kuće sam stavila losos u frižider, a cvijeće sam stavila u vazu. or
• Kod kuće sam stavila losos u frižider, a cvijeće u vazu sam stavila.

But that sounds more repetitive. The shorter version is very natural.

A often means and, but not exactly in the same way as English and.

It often links two things with a slight sense of contrast, comparison, or switch of topic.

Here:

• losos u frižider, a cvijeće u vazu

means something like:

• the salmon in the fridge, and the flowers in the vase
• or more literally, the salmon into the fridge, while the flowers into the vase

It separates the two objects and destinations clearly.

In many contexts:

• i = simple and
• a = and / while / whereas / but depending on context

Frižider is very common and widely understood. It is an everyday word for fridge/refrigerator.

You may also see:

• hladnjak

Both are used, though hladnjak is often felt to be more standard or formal, while frižider is extremely common in everyday speech.

So both of these are fine:

• Stavila sam losos u frižider.
• Stavila sam losos u hladnjak.

Yes, it is natural.

A native speaker could also say:

• Kod kuće sam stavila losos u frižider, a cvijeće u vazu.
• Stavila sam kod kuće losos u frižider, a cvijeće u vazu.
• Losos sam stavila u frižider, a cvijeće u vazu.

The original sentence sounds normal and clear. The main differences in other versions are about emphasis and word order, not basic meaning.

The structure is:

• Kod kuće = adverbial phrase (at home)
• sam stavila = past tense verb (I put; female speaker)
• losos = direct object
• u frižider = destination
• a = linking word
• cvijeće = second direct object
• u vazu = second destination

So the sentence is basically:

At home, I put [the salmon] [into the fridge], and [the flowers] [into the vase].

It is a nice example of how Croatian can leave out repeated verbs when the structure is clear.