Iza garaže su bušilica, čekić i mala kutija s čavlima.

Because iza takes the genitive case in Croatian.

• Base form: garaža = garage
• Genitive singular: garaže

So iza garaže means behind the garage.

This is something you just have to learn with the preposition: iza + genitive.

They are in the nominative, because they are the subject of the sentence.

Individually:

• bušilica = nominative singular
• čekić = nominative singular
• mala kutija = nominative singular

Even though each noun is singular, together they form a compound subject, which is why the verb is plural.

Because Croatian makes the verb agree with the whole subject, not with each item separately.

Here the subject is a list of three things:

• bušilica
• čekić
• mala kutija s čavlima

A list like that counts as plural, so you need su = are.

If there were only one item, you would use je:

• Iza garaže je bušilica.

This is due to Croatian word order and clitic placement.

The sentence begins with Iza garaže to set the location first. Then the short form su comes very early in the sentence, in the typical second-position clitic spot.

So:

• Iza garaže su bušilica, čekić i mala kutija s čavlima.

This is very natural Croatian.

English speakers often expect the subject first, but Croatian word order is much more flexible.

Yes. That is also grammatical.

The difference is mostly about focus:

• Iza garaže su... puts emphasis on where they are
• Bušilica, čekić i mala kutija s čavlima su iza garaže starts with what is there

Both are correct. Croatian often changes word order depending on what the speaker wants to highlight.

Because Croatian does not need a dummy subject like English there.

English says:

• There are tools behind the garage.

Croatian simply uses the verb to be:

• Iza garaže su...

So Croatian expresses the idea directly, without an extra word like there.

Because adjectives must agree with the noun in gender, number, and case.

Here:

• kutija is feminine
• it is singular
• it is in the nominative

So the adjective must match:

• mala kutija = small box

If the noun were masculine, the adjective would change:

• mali čekić = small hammer

If it were neuter:

• malo... would be used

The preposition s here means with, and it takes the instrumental case.

So:

• base noun: čavao = nail
• plural nominative: čavli = nails
• instrumental plural: čavlima

That gives:

• kutija s čavlima = a box with nails

This is a very common pattern:

• kava s mlijekom = coffee with milk
• čovjek s psom = man with a dog

Because s is the normal form, and sa is only used when it is easier or more natural to pronounce.

In this sentence, s čavlima is standard and natural.

You will often see sa:

• before certain consonant clusters
• in some fixed expressions, such as sa mnom

So the important thing to remember is:

• both mean with
• sa is mainly a pronunciation-friendly variant of s

This is a very common question for English speakers.

• č is a harder sound, roughly like ch in church
• ć is softer, and English does not have an exact equivalent

So čekić is approximately:

• CHE-kić, with a hard č at the start
• and a softer final ć

Also:

• čavlima begins with č
• bušilica has š, pronounced like sh

So in this sentence you hear several important Croatian consonants:

• č as in čekić, čavlima
• ć as in the final sound of čekić
• š as in bušilica

Because Croatian does not have articles.

So Croatian nouns appear without words like a or the:

• garaža
• bušilica
• čekić
• kutija

Whether something is understood as a box or the box depends on context.

This is a major difference from English, and it often feels strange at first, but it is completely normal in Croatian.

Not always. The form garaže can represent more than one grammatical form, depending on context.

For example, it can be:

• genitive singular of garaža
• nominative plural of garaža

But in this sentence, after iza, it must be genitive singular, because iza requires the genitive.

So context tells you which form it is.