Nova podstanarka kaže da joj stan odgovara, ali je kaucija jako visoka.

Because nova has to agree with podstanarka in gender, number, and case.

• podstanarka is feminine singular nominative
• so the adjective must also be feminine singular nominative
• that form is nova

Compare:

• novi podstanar = a new male tenant/subtenant
• nova podstanarka = a new female tenant/subtenant

So nova is simply the correct matching adjective form.

Yes. It is related to stan, which means apartment/flat.

• stan = apartment, flat
• podstanar = a male tenant/subtenant, especially someone renting a place to live
• podstanarka = the feminine form, a female tenant/subtenant

The ending -ka often makes a feminine noun from a masculine one:

• podstanar → podstanarka

So this sentence is specifically talking about a woman.

Kaže is the 3rd person singular present tense of kazati / reći, meaning to say.

Here it matches the subject nova podstanarka:

• ja kažem = I say
• ti kažeš = you say
• on/ona kaže = he/she says

Since podstanarka is she, Croatian uses kaže.

In Croatian, da often introduces a clause like English that.

So:

• kaže da... = she says that...

In English, that is often optional:

• She says the apartment suits her
• She says that the apartment suits her

In Croatian, da is very commonly used in this structure.

So:

• Nova podstanarka kaže da joj stan odgovara
  = The new tenant says that the apartment suits her

Joj means to her.

It is the dative singular form of the pronoun ona.

So in this sentence:

• joj stan odgovara literally means something like the apartment suits to her
• more natural English: the apartment suits her

This happens because the verb odgovarati takes the dative case when it means to suit / to be suitable for someone.

Useful comparison:

• on → mu = to him
• ona → joj = to her
• oni/one → im = to them

Good question. Odgovarati can mean different things depending on context.

Two common meanings are:

1. to answer / reply

   • Odgovara na pitanje. = He/She is answering a question.

2. to suit / fit / be suitable

   • Ovaj termin mi odgovara. = This time works for me.
   • Stan joj odgovara. = The apartment suits her.

In your sentence, it clearly means to suit / be suitable for, not to answer.

That is why joj is in the dative:

• odgovarati komu = to suit someone

Because with the meaning to suit, odgovarati works like this:

• the thing that suits someone is the subject
• the person it suits is in the dative

So:

• stan = subject, nominative
• joj = dative, to her
• odgovara = suits

Literally, the structure is closer to:

• The apartment is suitable to her

rather than:

• She suits the apartment

This is one of those verb patterns that English speakers simply need to learn.

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

So:

• stan can mean an apartment, the apartment, or just apartment
• kaucija can mean a deposit or the deposit

The exact meaning depends on context.

In this sentence, English naturally uses the:

• the apartment
• the deposit

But Croatian does not need a separate word for that.

This is about clitic word order.

Je here is a short unstressed form of the verb biti (to be). Short forms like je, sam, si, se, mi, joj, etc. are called clitics, and they often appear near the beginning of the clause.

So:

• ali je kaucija jako visoka is a very natural Croatian order

You may also hear or see:

• ali kaucija je jako visoka

That is also understandable, but the version with je earlier is very typical because clitics like to stand in an early position.

So the placement of je is mainly a matter of normal Croatian clitic placement, not a change in meaning.

Because visoka is the correct form to match kaucija.

Here:

• kaucija is feminine singular nominative
• after je, the adjective in this kind of predicate usually matches the subject in gender, number, and case
• so we get visoka

That is why the phrase is:

• kaucija je visoka = the deposit is high

Compare:

• visok stanar = a tall male tenant
• visoka kaucija = a high deposit

Even though English uses high for prices, fees, deposits, Croatian often uses visok / visoka / visoko in the same way.

Yes. Here jako means very.

So:

• jako visoka = very high

It strengthens the adjective visoka.

Common examples:

• jako dobro = very well
• jako skupo = very expensive
• jako visoka = very high

You may also learn vrlo, which also means very:

• jako visoka
• vrlo visoka

Both are correct. Jako is extremely common in everyday speech.

Yes. Croatian word order is more flexible than English word order, although not completely free.

For example, these are possible:

• Nova podstanarka kaže da joj stan odgovara, ali je kaucija jako visoka.
• Nova podstanarka kaže da stan njoj odgovara, ali je kaucija jako visoka.
• Nova podstanarka kaže da joj odgovara stan, ali je kaucija jako visoka.

But they do not all sound equally neutral. The original sentence sounds natural and neutral.

Croatian often changes word order for:

• emphasis
• contrast
• information structure
• clitic placement

So as a learner, it is best to treat the original version as a very good standard model.

Yes, in this sentence ali means but.

It connects two ideas:

• the apartment suits her
• the deposit is very high

So the full structure is:

• X, ali Y = X, but Y

It signals contrast:

• one thing is positive
• the other is a problem

That is exactly how English but works here.