Kondukter nam je objasnio da je presjedanje kratko i da moramo brzo prijeći na drugi peron.

Nam means to us. It is the unstressed dative form of the 1st person plural pronoun.

Here, the verb objasniti often works like explain something to someone, so:

• nam = to us
• the whole da... clause = the thing that was explained

A fuller, stressed form would be nama, but in normal sentences Croatian usually uses the clitic nam.

Because nam and je are clitics, and Croatian clitics normally go in second position in the clause.

So after the first stressed element Kondukter, the clitic cluster appears:

• Kondukter nam je objasnio

This is standard and natural.
Kondukter je nam objasnio sounds wrong in standard Croatian word order.

The object is not a single noun. It is the whole content clause introduced by da:

• da je presjedanje kratko i da moramo brzo prijeći na drugi peron

So the structure is basically:

• The conductor explained to us
  • that...

This is very common in Croatian. After verbs like reći, znati, misliti, objasniti, the thing said/thought/explained is often expressed with a da clause.

Objasnio is the masculine singular l-participle, used with je to form the past tense.

So:

• je objasnio = explained / has explained

It agrees with the subject kondukter, which is masculine singular.

Compare:

• kondukter je objasnio
• kondukterka je objasnila
• ljudi su objasnili

Because the two instances of je are doing different jobs.

1. In nam je objasnio, je is an auxiliary verb helping form the past tense.
2. In da je presjedanje kratko, je is the ordinary present tense of biti = is.

So:

• je objasnio = explained
• je kratko = is short

They look the same, but they are not functioning in the same way.

Presjedanje is a verbal noun meaning something like changing trains/buses, transfer, or connection change.

It comes from a verb meaning to change from one vehicle to another. Croatian often forms nouns like this with endings such as -anje or -enje, turning an action into a thing or event.

Grammatically, presjedanje is:

• singular
• neuter

That matters for agreement with adjectives like kratko.

Because presjedanje is a neuter noun, and the adjective has to agree with it.

So:

• masculine: kratak
• feminine: kratka
• neuter: kratko

Since the sentence says presjedanje je..., the correct form is:

• presjedanje je kratko

Croatian often repeats da when two content clauses are linked:

• da je presjedanje kratko
• i da moramo brzo prijeći na drugi peron

This is very natural and standard. English can sometimes omit the second that, but Croatian often prefers to keep the second da for clarity and smooth structure.

So the repeated da is not redundant; it is normal Croatian syntax.

Because Croatian often leaves subject pronouns unstated when the verb ending already makes the subject clear.

Moramo already means we must:

• mor- = verb stem
• -amo = 1st person plural ending

So mi is not necessary unless you want emphasis or contrast:

• Mi moramo... = We have to... / We are the ones who have to...

In a neutral sentence, just moramo is enough.

Because prijeći is perfective and fits a single completed action: crossing over to the other platform.

Here the idea is that they need to complete that action quickly. So prijeći is the natural choice.

Very roughly:

• prijeći = to cross over, successfully get across once
• prelaziti = to be crossing, to cross repeatedly, or in a more ongoing/general sense

In this situation, the perfective verb sounds more appropriate because the transfer is short and the move has to be completed.

Because with na, Croatian distinguishes between:

• movement toward a place → accusative
• location at a place → locative

Here the meaning is movement: they must go over to another platform.

So Croatian uses the accusative:

• na drugi peron

If the meaning were location, it would be:

• na drugom peronu = on the other platform

It is accusative singular.

However, peron is a masculine inanimate noun, and in Croatian the accusative singular of masculine inanimate nouns usually looks the same as the nominative.

So:

• nominative: drugi peron
• accusative: drugi peron

That is why the form does not visibly change here.

Because Croatian does not have articles like the and a/an.

So kondukter can mean the conductor or a conductor, depending on context. The same applies to many nouns in Croatian.

If speakers need extra clarity, they can use other words such as demonstratives, but very often context is enough. In this sentence, the situation makes it clear which conductor is meant.