Ako se iselite prije kraja ugovora, najmodavka može zadržati dio kaucije.

The se is part of the verb here. Iseliti se / iseliti in this context usually means to move out.

• iseliti can mean to move something/someone out
• iseliti se means to move out oneself

So:

• Ako se iselite... = If you move out...

Without se, the meaning would sound incomplete or would suggest moving someone or something else out.

Iselite is the 2nd person plural present tense form of iseliti se.

It can mean:

• you (plural) move out
• or you (formal singular) move out

Croatian uses the plural form to address one person politely, just like many European languages do.

So in a housing or contract context, Ako se iselite... can easily mean:

• If you move out... addressed formally to one tenant

Croatian commonly uses the present tense after ako for real future conditions, much like English does in sentences such as If you leave early, ...

So:

• Ako se iselite prije kraja ugovora... = If you move out before the end of the contract...

This is normal Croatian usage. You do not need a future tense here.

Because prije requires the genitive case.

So:

• prije = before
• kraj = end
• kraja = genitive singular of kraj
• ugovor = contract
• ugovora = genitive singular of ugovor

The phrase works like this:

• prije kraja = before the end
• kraja ugovora = the end of the contract

So both nouns appear in the genitive:

• prije kraja ugovora

Najmodavka is a feminine noun meaning female landlord / landlady.

Related forms:

• najmodavac = male landlord
• najmodavka = female landlord

In real-life Croatian, people may also use other words depending on context, but najmodavac / najmodavka is a correct and fairly formal/legal choice.

So this sentence specifically refers to a female landlord.

Može zadržati means can keep or may retain.

It is made of:

• može = can / is able to / may
• zadržati = to keep / retain / hold back

So:

• najmodavka može zadržati... = the landlord can keep... or in a more legal style, the landlord may retain...

After modal verbs like moći (can / be able to), Croatian normally uses the infinitive.

Examples:

• mogu doći = I can come
• možete platiti = you can pay
• može zadržati = can keep

So this is a very standard structure:

• može + infinitive

Because dio is followed by the genitive when it means part of something.

So:

• dio = part
• kaucija = deposit
• kaucije = genitive singular

Therefore:

• dio kaucije = part of the deposit

This is a very common Croatian pattern:

• čaša vode = a glass of water
• komad kruha = a piece of bread
• dio novca = part of the money

Yes. Kaucija is the standard word for a deposit, especially in rental contexts.

So in housing language:

• platiti kauciju = to pay a deposit
• vratiti kauciju = to return the deposit
• zadržati dio kaucije = to keep part of the deposit

Yes, Croatian word order is more flexible than English word order.

This version:

• Ako se iselite prije kraja ugovora, najmodavka može zadržati dio kaucije.

is neutral and natural.

You could rearrange parts for emphasis, for example:

• Najmodavka može zadržati dio kaucije ako se iselite prije kraja ugovora.

That still means the same thing. Croatian often moves things around to change emphasis, while the cases help show the grammatical relationships.

Yes. Both verbs are perfective, which fits this sentence well because it refers to a completed action/result.

• iseliti se = to move out as a completed act
• zadržati = to keep/retain with focus on the result

In conditional or legal-style sentences, perfective verbs are often used when the speaker is talking about a specific completed event:

• if you move out
• the landlord may keep

An imperfective version would give a different nuance and would usually not be the most natural choice here.

It can be understood as either, depending on style.

• In everyday English: can keep
• In legal or contract-style English: may retain

In Croatian, može often covers both practical possibility and permission/right, so context tells you which nuance is strongest. In this sentence, because it is about a contract, may retain is often the best interpretation.

Yes, but prije kraja ugovora is very natural and standard.

Another possible phrasing is:

• prije nego što ugovor završi = before the contract ends

But in formal, written, or contractual language, the noun phrase prije kraja ugovora is especially common and concise.