Završetak radova kasni u mjeri u kojoj ima dodatnih radova.

Because the grammatical subject is završetak, not radova.

• završetak = completion / ending
• radova = of the works / of the tasks

So the structure is:

• Završetak radova = the completion of the works

Since završetak is singular, the verb is singular too:

• završetak ... kasni = the completion ... is delayed / is late

English speakers often focus on the nearest noun, but in Croatian the verb agrees with the true subject, not just the closest plural noun.

It is in the genitive plural because završetak normally takes a genitive complement: completion of something.

Compare:

• završetak projekta = completion of the project
• završetak radova = completion of the works

So here:

• radovi is the basic plural form
• radova is the genitive plural form

This is a very common pattern with verbal nouns in Croatian.

Kasniti basically means to be late or to be delayed.

In this sentence, kasni is best understood as:

• is delayed
• or literally is running late

Croatian often uses an active-looking verb where English might prefer a passive expression. So:

• Završetak radova kasni
  literally: The completion of the works is late
• natural English: The completion of the works is delayed

This is a fairly formal expression meaning:

• to the extent that
• insofar as
• in the measure that
• sometimes in proportion to how much

So u mjeri u kojoj ima dodatnih radova means something like:

• to the extent that there is additional work
• in proportion to the amount of additional work

It is not a casual everyday phrase; it sounds more administrative, legal, or technical.

Kojoj refers back to mjeri.

The phrase is:

• u mjeri = in the extent / in the measure
• u kojoj = in which

So literally the structure is:

• u mjeri u kojoj ... = in the measure in which ...

Grammatically:

• mjera is feminine singular
• after u, here it is in the locative
• therefore the relative pronoun must match it: kojoj

So kojoj is feminine singular locative, agreeing with mjeri.

Because the sentence contains two linked parts:

1. u mjeri = a prepositional phrase
2. u kojoj = a relative clause referring back to mjeri

So the first u belongs to mjeri, and the second u belongs to kojoj.

This is normal in Croatian. It may feel repetitive to an English speaker, but it is a standard structure.

Here ima is being used in an existential sense, meaning there is / there are.

So:

• ima dodatnih radova = there is/are additional work(s)

This is a very common Croatian pattern. It does not mean someone has additional works here. It means that additional works exist / are present.

The singular form ima is normal in this impersonal existential use, even when English would say there are.

This time it is genitive for a different reason.

In ima dodatnih radova, the noun phrase after existential ima is commonly in the genitive:

• ima problema = there are problems
• ima ljudi = there are people
• ima dodatnih radova = there is/are additional works

So:

• radova = genitive plural of radovi
• dodatnih agrees with it, so it is also genitive plural

This is different from the first radova in završetak radova, even though the form happens to be the same.

Yes, in this kind of context radovi usually means:

• works
• construction works
• tasks
• operations
• work items

This is common in technical, construction, project-management, and legal language.

So dodatni radovi usually means additional works or extra work items, not artistic works like books or paintings.

It sounds formal, especially because of u mjeri u kojoj.

You could expect this kind of sentence in:

• contracts
• project reports
• construction documentation
• legal or administrative writing

In everyday speech, people would often say something simpler, for example:

• Završetak radova kasni ovisno o tome koliko ima dodatnih radova.
• Što ima više dodatnih radova, to završetak više kasni.

The original sentence is correct, but stylistically formal.

Yes, Croatian word order is fairly flexible.

The original version is neutral and formal:

• Završetak radova kasni u mjeri u kojoj ima dodatnih radova.

But you could also say:

• U mjeri u kojoj ima dodatnih radova, završetak radova kasni.

That version puts more focus on the condition/extent first.

The original order is probably the most natural in official or written style.

Because Croatian has no articles like English a/an/the.

So nouns such as:

• završetak
• radova

do not need separate words for the.

Whether English translates them as the completion, completion, the works, or works depends on context, not on an article in Croatian.

That is why a Croatian sentence can look more compact than its English equivalent.