Nadležno tijelo provjerava moju prijavu.

Because nadležno is an adjective agreeing with tijelo, and tijelo is neuter singular nominative.

In Croatian, adjectives must match the noun in:

• gender
• number
• case

So:

• nadležan = masculine singular
• nadležna = feminine singular
• nadležno = neuter singular

Since tijelo is a neuter noun, you get:

• nadležno tijelo = the competent / responsible authority

Literally, yes: tijelo often means body.

But in this sentence it is being used in an administrative/legal sense, where it means something like:

• authority
• body
• official institution
• competent authority

So nadležno tijelo is a common formal phrase meaning the competent authority or the relevant authority.

This is standard bureaucratic Croatian.

Because prijavu is the direct object of the verb provjerava, so it must be in the accusative case.

The noun is:

• prijava = nominative singular
• prijavu = accusative singular

And the possessive adjective moja must agree with it, so it also changes:

• moja prijava = my application/report (subject form)
• moju prijavu = my application/report (object form)

So in this sentence:

• Nadležno tijelo = subject
• provjerava = verb
• moju prijavu = direct object

Because prijava is a feminine noun, and feminine nouns ending in -a usually change to -u in the accusative singular.

So:

• nominative: prijava
• accusative: prijavu

This is a very common pattern in Croatian:

• knjiga → knjigu
• žena → ženu
• molba → molbu
• prijava → prijavu

Since provjeravati / provjerava takes a direct object, the accusative is required.

Prijava has several possible meanings depending on context, such as:

• application
• registration
• report
• submission
• sometimes even complaint or notification

In official or administrative contexts, moja prijava often means:

• my application
• my submitted form/request

The exact English translation depends on the situation, but the Croatian grammar stays the same.

Provjerava is present tense, 3rd person singular.

It comes from the verb provjeravati / provjeriti.

Here it means:

• checks
• is checking

Croatian present tense can often correspond to either simple present or present continuous in English, depending on context.

So Nadležno tijelo provjerava moju prijavu could mean:

• The competent authority checks my application
• The competent authority is checking my application

This is about aspect, which is very important in Croatian.

• provjeravati = imperfective verb
  
  • ongoing, repeated, or process-focused
• provjeriti = perfective verb
  
  • completed action

So:

• provjerava = is checking / checks
• provjeri can be a present-form perfective verb, but perfective present usually refers to a future completed action in meaning, not an ongoing present action.

In a sentence describing a process happening now, provjerava is the natural choice.

No, Croatian word order is fairly flexible, because case endings show grammatical roles.

The neutral, standard order here is:

• Nadležno tijelo = subject
• provjerava = verb
• moju prijavu = object

So:

• Nadležno tijelo provjerava moju prijavu.

But other orders are possible for emphasis, for example:

• Moju prijavu provjerava nadležno tijelo.
  Emphasis on my application

• Moju prijavu nadležno tijelo provjerava.
  Also possible, though more marked

The original sentence is the most neutral and typical in formal writing.

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

So Croatian simply says:

• nadležno tijelo
  not
• the competent authority

Whether something is definite or indefinite is usually understood from:

• context
• word order
• the situation
• sometimes added words

So English needs the, but Croatian does not.

Yes, you could say:

• Nadležno tijelo provjerava prijavu.

That would mean:

• The competent authority is checking the application

But moju prijavu specifically means my application.

Including moju is necessary if you want to make it clear whose application it is. It may also add a slight emphasis: my application.

Yes, very formal.

Words like:

• nadležno tijelo
• prijava
• provjerava

are common in:

• official notices
• government websites
• application procedures
• legal or administrative communication

In everyday speech, people might use simpler wording depending on the context, but this sentence sounds completely normal in bureaucratic Croatian.

You know it mainly from the case endings.

• nadležno tijelo is in the nominative, which is the usual case for the subject
• moju prijavu is in the accusative, which is the usual case for the direct object

Also, the verb agrees with the subject:

• provjerava = he/she/it checks
• tijelo is singular, so the singular verb form fits

So even if the order changed, the endings still tell you who is doing the action and what is being checked.

A rough pronunciation guide is:

• Nadležno ≈ NAH-dlezh-no
• tijelo ≈ TYE-lo
• provjerava ≈ pro-vye-RA-va
• moju ≈ MO-yu
• prijavu ≈ pri-YA-vu

A rough full version:

NAH-dlezh-no TYE-lo pro-vye-RA-va MO-yu pri-YA-vu

A few useful sound notes:

• ž sounds like the s in measure
• j sounds like English y
• lj is a soft sound, somewhat like lli in million for many learners

Croatian spelling is quite phonetic, so pronunciation is usually more predictable than in English.