U kuhinji je bio mali požar, ali su ga brzo ugasili.

Because after u meaning in for a location, Croatian uses the locative case.

• kuhinja = the basic dictionary form, nominative
• u kuhinji = in the kitchen (location, locative)

A very useful contrast is:

• u kuhinji = in the kitchen (already there)
• u kuhinju = into the kitchen (movement toward it)

So here u kuhinji is used because the fire was located there.

This is the past tense. Croatian commonly forms the past with:

• a short form of biti (je, su, etc.)
• plus the l-participle

Here:

• je = is/has as the past auxiliary for he/it
• bio = masculine singular past participle

So je bio means was.

It is bio because požar is a masculine singular noun.

Compare:

• požar je bio = the fire was
• vatra je bila = the fire/flame was
• selo je bilo = the village was

Because je is a clitic. In Croatian, clitics usually go in the second position of the clause.

So:

• U kuhinji je bio mali požar.

The first unit is U kuhinji, and the clitic je comes right after it.

This is a very common Croatian pattern. English speakers often expect a more fixed English-style order, but Croatian clitic placement follows its own rules.

Because Croatian uses case endings, not just word order, to show grammatical roles.

Here:

• požar is in the nominative, so it is the subject
• bio agrees with it in masculine singular

So even though the noun comes later in the sentence, it is still the thing that was there.

Croatian word order is more flexible than English word order.

Because adjectives must agree with the noun they describe.

požar is:

• masculine
• singular
• nominative

So the adjective must match:

• mali požar = small fire

Compare:

• mala kuhinja = small kitchen
• malo selo = small village
• mali požari = small fires

Croatian does not need a dummy subject like English there.

English says:

• There was a small fire in the kitchen.

Croatian simply says:

• U kuhinji je bio mali požar.

Literally, it is closer to:

• In the kitchen was a small fire.

So Croatian does not insert a meaningless there the way English does.

ga is the short accusative pronoun meaning him/it, and here it means it.

It refers back to požar.

Why ga?

• požar is masculine singular
• it is the direct object of ugasili in the second clause
• so the pronoun becomes ga

Full version:

• ugasili su požar = they extinguished the fire

With a pronoun:

• ugasili su ga = they extinguished it

Because Croatian often omits subject pronouns when they are understood from the verb form.

Here:

• su ... ugasili = they extinguished

So an explicit oni (they) is not necessary.

Croatian does this all the time:

• Došli su. = They came.
• Vidjela je. = She saw.
• Rekli smo. = We said.

The verb ending already tells you the person and number.

Because the hidden subject is plural: they.

So the participle must match that subject:

• ugasio = he extinguished
• ugasila = she extinguished
• ugasili = they extinguished (masculine or mixed group; also the usual default if unspecified)
• ugasile = they extinguished (all-female group)

Since the sentence does not specify who they were, ugasili is the normal default form.

Both su and ga are clitics, and Croatian clitics tend to stay together near the beginning of the clause in a fairly fixed order.

So:

• ali su ga brzo ugasili = natural standard order

English speakers often want to move these little words around freely, but in Croatian clitic order is much more restricted.

The important thing to remember here is that su ga is the normal pattern.

brzo is an adverb meaning quickly. It modifies the verb ugasili.

So:

• brzo ugasili = extinguished quickly

Unlike adjectives, adverbs do not change form here to match gender or number.

Word order can shift a bit for emphasis, for example:

• Ali su ga brzo ugasili.
• Ali brzo su ga ugasili.

But the original version is very natural.

Because požar usually means a fire as an incident, especially one that is dangerous or needs to be put out.

• požar = fire, blaze, fire incident
• vatra = fire/flame more generally

So a small kitchen fire as an event is very naturally mali požar.

If you used vatra, it could sound more like talking about the flames themselves rather than the whole incident.

Yes. Croatian word order is flexible, although some versions sound more natural than others and may shift emphasis.

For example:

• U kuhinji je bio mali požar, ali su ga brzo ugasili.
• Mali požar je bio u kuhinji, ali su ga brzo ugasili.

The original sentence puts the location first, which is very natural if you are setting the scene.

So in Croatian, changing word order often changes focus or emphasis, not the basic meaning.