Auto nam se pokvario na autocesti, pa smo zvali pomoć.

Yes. Auto is the common short form of automobil. It is very natural in everyday Croatian, much like car is more common than automobile in English.

It is also treated as a masculine singular noun, which is why the past form later is pokvario.

Nam is the dative form of mi (we/us), and here it works as a kind of dative of possession or affected person.

So Auto nam se pokvario literally feels like:

The car broke down on us

or

Our car broke down

Croatian often uses this structure instead of a possessive adjective like naš. You could also say Naš auto se pokvario, but auto nam se pokvario is very natural and often sounds more personal, as if emphasizing that this happened to us.

Because the verb here is pokvariti se, which means to break down, to become broken, or to stop working.

Compare:

• pokvariti nešto = to break/spoil something
• pokvariti se = to break down / become spoiled

So:

• Pokvario sam radio. = I broke the radio.
• Radio se pokvario. = The radio broke down.

In your sentence, the car is not being actively broken by someone; it simply stopped working, so se is required.

Because pokvario agrees with auto.

In Croatian past tense, the -l form agrees in gender and number with the subject. Since auto is masculine singular, you get:

Auto se pokvario.

If the subject were a neuter noun, you would get pokvarilo, and with a feminine noun you would get pokvarila.

No. It is not the same as an English passive like was broken.

Here, pokvario se is a reflexive/pronominal verb meaning broke down or became broken. It describes a change of state of the subject.

So Auto se pokvario means:

The car broke down

not

The car was broken by someone.

Because Croatian clitics have a fairly fixed order, and nam normally comes before se.

So the natural order is:

Auto nam se pokvario

not

Auto se nam pokvario

Both nam and se are clitics, and Croatian tends to place them in a set sequence. For learners, it is best to memorize nam se as the normal order here.

Because Croatian clitics usually go in the second position in the clause.

So in:

Auto nam se pokvario

the first stressed word is Auto, and then the clitic cluster comes right after it: nam se.

This second-position rule is very important in Croatian word order.

It is locative after na, because the meaning is location:

on the motorway / on the highway

So:

• na autocesti = on the motorway (location)
• na autocestu = onto the motorway (motion toward it)

Here the car broke down while already being there, so Croatian uses the locative: na autocesti.

Pa here means something like:

so and so then as a result

It connects the two events:

1. the car broke down
2. we called for help

So pa smo zvali pomoć means so we called for help.

It is a very common and natural connector in Croatian.

Smo zvali is the Croatian past tense, built with:

• the auxiliary smo = we are / we have in this structure
• the past participle zvali

Together:

smo zvali = we called

Croatian often leaves out subject pronouns when they are obvious from the verb form. Since smo already shows we, there is no need to say mi unless you want emphasis.

So:

• smo zvali pomoć = we called for help
• mi smo zvali pomoć = we called for help with extra emphasis on we

Because the past participle agrees with the subject.

Zvali is used for:

• a group of men, or
• a mixed group, or
• a group of unspecified gender in many neutral examples

If the speakers were all female, it would be:

zvale smo pomoć

So this part tells you something about the subject group, not about pomoć.

It is the direct object of zvati, so it is in the accusative.

However, the noun pomoć has the same form in nominative and accusative singular, so it stays pomoć.

That is why you see:

zvati pomoć = to call for help

even though it is functioning as the object.

Yes, it is normal Croatian.

Croatian often says zvati pomoć, where English more naturally says call for help. In context, pomoć can mean general help, emergency help, or assistance such as roadside assistance.

So the Croatian phrasing is natural, even if the English structure is a little different.

Yes. You could say:

Auto se pokvario na autocesti, pa smo zvali pomoć.

That simply means:

The car broke down on the motorway, so we called for help.

Adding nam makes it more personal and often suggests our car or the car we were using, with the sense that this happened to us.