Otkazivanje leta nakon dužeg kašnjenja leta je problem.

Otkazivanje is a verbal noun: it turns the action to cancel into a thing or concept, like cancellation in English.

So instead of saying something like They cancel the flight, the sentence talks about the cancellation of the flight as an abstract event:

• otkazati let = to cancel a flight
• otkazivanje leta = the cancellation of the flight / cancelling a flight

In this sentence, otkazivanje leta nakon dužeg kašnjenja leta is the subject of the sentence.

Because after a verbal noun like otkazivanje, the thing affected by the action is commonly put in the genitive.

So:

• otkazati let = to cancel a flight
  
  • let is the direct object
• otkazivanje leta = cancellation of a flight
  
  • leta is genitive singular

This is very common in Croatian with nouns ending in -nje or -vanje.

Because the preposition nakon always requires the genitive case.

So:

• nakon kašnjenja = after a delay
• nakon sastanka = after the meeting
• nakon ručka = after lunch

That is why the base noun kašnjenje becomes kašnjenja.

Because dužeg has to match kašnjenja in case, number, and gender.

Here:

• kašnjenja is genitive singular
• kašnjenje is neuter
• the adjective is therefore also in genitive singular neuter

The adjective is based on duži = longer, and in this form it becomes dužeg.

So:

• nakon dužeg kašnjenja = after a longer delay

Yes. Dužeg is the comparative form, so literally it means longer.

However, in real usage, Croatian sometimes uses a comparative like this in a slightly looser way, where English might say:

• after a longer delay
• after a fairly long delay
• after a prolonged delay

You could also say nakon dugog kašnjenja = after a long delay. That version may feel more straightforward to learners.

So both are possible, but the nuance is slightly different:

• dugog = long
• dužeg = longer / somewhat prolonged

It is a bit repetitive, yes.

The second leta makes it explicit that the delay is the delay of the flight. Grammatically, that is fine:

• kašnjenje leta = the delay of the flight

But because leta already appeared earlier in otkazivanje leta, many speakers would probably drop the second one if the meaning is already clear:

• Otkazivanje leta nakon dužeg kašnjenja je problem.

That usually sounds more natural and less heavy.

It is grammatical and understandable, but it sounds a bit formal, abstract, and repetitive.

A more natural version would often be:

• Otkazivanje leta nakon dužeg kašnjenja je problem.

If you wanted a different style, you could also say:

• Problem je otkazivanje leta nakon dužeg kašnjenja.
• Otkazati let nakon dužeg kašnjenja predstavlja problem.

So the original is not wrong, but it is not the smoothest everyday phrasing.

Because Croatian has no articles.

So problem can mean:

• a problem
• the problem

The exact meaning depends on context.

That is normal in Croatian. You do not need a word corresponding to a or the.

The whole phrase is in the nominative singular, because it is the subject of the sentence.

The head word is otkazivanje, and that noun is nominative singular.

Inside that subject, some dependent words are in the genitive:

• leta after otkazivanje
• kašnjenja after nakon
• leta after kašnjenja

So the full subject is nominative as a phrase, even though it contains several genitive forms inside it.

Yes. Croatian word order is fairly flexible, and changing it often changes emphasis rather than basic meaning.

For example:

• Otkazivanje leta nakon dužeg kašnjenja leta je problem.
  Neutral, formal statement.

• Nakon dužeg kašnjenja leta, otkazivanje leta je problem.
  Emphasizes the time sequence after a long delay.

• Problem je otkazivanje leta nakon dužeg kašnjenja leta.
  Emphasizes problem first.

The original order is fine, but not the only possible one.

Je is the present tense of biti = to be.

In the sentence, it links the subject and the predicate:

• Otkazivanje leta nakon dužeg kašnjenja leta = subject
• je = is
• problem = predicate noun

So the structure is simply:

• X je Y = X is Y

Croatian often places these short forms of biti early in the clause, but here the whole subject phrase comes first, and then je follows it naturally.

Yes, often you can.

• nakon dužeg kašnjenja
• poslije dužeg kašnjenja

Both mean after a longer delay and both take the genitive.

The difference is mostly in style:

• nakon often sounds a bit more neutral or formal
• poslije is very common in everyday speech

So nakon is perfectly good here, especially in a formal sentence.