U prijavi krađe piše: bicikl je pronađen; potraga završava.

Because the preposition u means in here, so it takes the locative case.

The noun prijava changes like this:

• nominative: prijava
• locative singular: prijavi

So u prijavi means in the report.

Because krađe is the genitive singular of krađa.

In Croatian, one noun often follows another in the genitive to show what something is about:

• prijava krađe = report of a theft or the theft report

So:

• krađa = theft
• krađe = of theft

This is a very common pattern in Croatian.

Here piše does not mean that someone is physically writing at that moment. In this kind of sentence, piše means something like it says or it is written.

So U prijavi krađe piše: means:

• In the theft report, it says:
• or The theft report says:

This impersonal use is very common when referring to written text.

Croatian often allows this kind of impersonal expression.

English uses it says, where it is a kind of grammatical placeholder. Croatian simply uses piše without needing an equivalent placeholder.

So the idea is:

• piše = it says / it is written

The context tells you that the source is u prijavi krađe.

The colon introduces the exact content of what is written.

So the structure is:

• U prijavi krađe piše: = In the theft report it says:
• then comes the message itself: bicikl je pronađen; potraga završava.

This works very much like English.

Bicikl je pronađen is a passive-style or result-focused way of speaking.

It focuses on the bicycle and the outcome:

• bicikl je pronađen = the bicycle has been found / was found

By contrast:

• pronašli su bicikl = they found the bicycle

The version in your sentence sounds more official, neutral, and report-like, which fits the context of a written report.

Pronađen is the passive participle of the verb pronaći.

In bicikl je pronađen, it combines with je to make a passive/resultative meaning:

• je pronađen = has been found / was found

It also behaves a bit like an adjective, so it must agree with the noun in gender and number.

Because bicikl is a masculine singular noun.

So the participle must match it:

• masculine singular: pronađen
• feminine singular: pronađena
• neuter singular: pronađeno
• plural masculine animate/inanimate as appropriate: pronađeni, etc.

Examples:

• bicikl je pronađen
• torba je pronađena
• pismo je pronađeno

Croatian often uses the present tense in notices, reports, headlines, and official-style statements to describe the current status or an immediate development.

So potraga završava can mean:

• the search ends
• the search is ending
• the search is coming to an end

It sounds concise and report-like.

A different version would be:

• potraga je završena = the search has been concluded / is concluded

That version focuses more on the completed result.

Because završavati / završiti can be used without se when something comes to an end.

So:

• potraga završava = the search is ending

This is normal Croatian.

You may also hear forms with se in other contexts, but here završava without se is perfectly natural and direct.

The semicolon links two closely related statements that are stronger than a comma but still belong together.

Here the two ideas are:

• the bicycle has been found
• the search is ending

They are clearly connected, so the semicolon works well in a formal written style.

A period could also be possible, but the semicolon keeps the statements tightly connected.

No, Croatian word order is fairly flexible, but this order is the most neutral here.

• bicikl je pronađen sounds natural and straightforward

Other orders may be possible in special contexts, but they would usually add emphasis or sound less neutral.

In a formal report, the sentence uses a very standard, unmarked order.

Croatian has no articles like English the and a.

So:

• bicikl can mean a bicycle or the bicycle
• prijava krađe can mean a theft report or the theft report

The exact meaning comes from context. In this sentence, the context makes the reference specific enough, so English naturally adds the where needed.