Za državljanstvo traže još jedan dokument, ali ga danas nemam sa sobom.

Croatian often leaves out subject pronouns because the verb ending already tells you the person and number.

Traže is 3rd person plural of tražiti, so the subject is understood as they.

In this sentence, they is not a specific group you already know; it is an indefinite they, meaning something like the office / the authorities / the people handling the application.

So this is very natural Croatian:

• Traže još jedan dokument. = They are asking for / requiring one more document.

If you said Oni traže, that would sound more explicit or contrastive, as if you really wanted to stress they.

The verb tražiti has a few related meanings, including:

• to look for
• to ask for
• to demand / require

Here it means to ask for or to require.

So in a bureaucratic context, traže još jedan dokument means:

• they are asking for one more document
• they require one more document

It does not mean they are physically searching for the document in this sentence.

Here za means for in the sense of for the purpose of / in connection with.

The preposition za takes the accusative here.

Državljanstvo is a neuter singular noun, and for many neuter nouns the nominative and accusative forms are the same, so:

• nominative: državljanstvo
• accusative: državljanstvo

So za državljanstvo means:

• for citizenship
• for the citizenship process/application, depending on context

Još jedan means one more or another.

• jedan = one
• još = more / still / additional, depending on context

Together:

• još jedan dokument = one more document / another document

You need both words because jedan dokument is just one document, while još jedan dokument adds the idea of an additional one.

Croatian does not have articles like a and the.

Definiteness is usually understood from:

• context
• word order
• demonstratives such as taj, ovaj, onaj
• numbers or other modifiers

Here, još jedan dokument clearly means one more document / another document, so English naturally uses a or another.

If Croatian wanted to be more specific, it might say something like:

• taj dokument = that document
• ovaj dokument = this document

Because dokument is the direct object of traže, it is in the accusative singular.

But dokument is a masculine inanimate noun, and for masculine inanimate nouns, the accusative singular is usually the same as the nominative singular.

So:

• nominative: dokument
• accusative: dokument

That is why the form does not change here.

Compare:

• Vidim dokument. = I see the document.
• Traže dokument. = They are asking for the document / a document.

Ga is an unstressed object pronoun. Here it means him/it, and it refers to dokument.

Because dokument is:

• singular
• masculine
• inanimate

the correct accusative pronoun is ga.

So:

• dokument → ga
• ali ga danas nemam = but I don’t have it today

Croatian often replaces a repeated noun with a short clitic pronoun like this, just as English uses it.

Because ga is a clitic: an unstressed short word that usually appears very early in the clause.

In Croatian, clitic pronouns such as ga, mi, ti, se, je normally go near the beginning of the clause, rather than in the more English-like position you might expect.

So:

• ali ga danas nemam is very natural

English speakers often want to place it later, but Croatian prefers the short pronoun early.

This early placement is one of the most important word-order habits to get used to in Croatian.

Because the verb here is imati = to have.

Its negative forms are:

• imam = I have
• nemam = I do not have

Nisam is the negative of biti = to be:

• jesam = I am
• nisam = I am not

So:

• nemam dokument = I do not have the document
• nisam doktor = I am not a doctor

Sa sobom literally means with oneself, but in normal English it is usually translated as:

• with me
• on me
• with you / with him / with her, depending on the subject

In this sentence:

• nemam ga sa sobom = I don’t have it with me

It is a very common expression for carrying something or having it in your possession at the moment.

A close alternative is:

• Nemam ga kod sebe. = I don’t have it on me / with me.

Because sa sobom is the normal reflexive expression when the thing is with the same person who is the subject.

Here the subject is I, so:

• nemam ga sa sobom = I don’t have it with me

If you said sa mnom, that usually means together with me in a more literal sense, not the usual idiom for possession/carrying.

So for this kind of idea, Croatian strongly prefers:

• imam ga sa sobom
• nemam ga sa sobom

rather than sa mnom.

Both s and sa mean with, but sa is used in certain situations for easier pronunciation.

It is especially common:

• before words beginning with s, z, š, ž
• before some pronouns, including sobom, mnom, tobom

So:

• sa sobom is the normal form
• sa mnom is the normal form

Using s sobom would sound awkward and is not the standard choice here.