Naša nova podstanarka želi se useliti već sljedeći tjedan.

Podstanarka means a female tenant / lodger, especially someone who is renting a place to live from someone else.

It is built from:

• podstanar = a male tenant
• podstanarka = a female tenant

So the sentence is specifically talking about a woman.

Yes. Podstanarka is explicitly feminine.

The masculine form is podstanar.

For example:

• naš novi podstanar = our new male tenant
• naša nova podstanarka = our new female tenant

Croatian usually marks gender much more clearly than English does.

Because they have to agree with podstanarka in:

• gender: feminine
• number: singular
• case: nominative

So:

• naša = our, feminine singular nominative
• nova = new, feminine singular nominative
• podstanarka = feminine singular noun in nominative

If the noun were masculine, the forms would change:

• naš novi podstanar

This kind of agreement is very important in Croatian.

Because Croatian does not use articles like English does.

So Croatian does not have separate words equivalent to:

• the
• a / an

Whether something is definite or indefinite is usually understood from context, or shown in other ways.

In this sentence, naša already makes the noun phrase feel definite:

• naša nova podstanarka = our new tenant

So English needs an article, but Croatian does not.

Želi is the 3rd person singular present tense of željeti, which means to want.

It matches the subject naša nova podstanarka, which is:

• one person
• feminine, but the verb form itself is just 3rd person singular

Some present-tense forms of željeti are:

• želim = I want
• želiš = you want
• želi = he/she/it wants
• želimo = we want
• želite = you all / you formal want
• žele = they want

So želi means she wants here.

Because the verb is useliti se, which means to move in.

Here, se is part of the verb expression. In Croatian, many verbs are used with se, and the meaning can change if you remove it.

Compare:

• useliti se = to move in
• useliti nekoga = to settle / move someone in

So in this sentence, the tenant wants to move in herself, which is why se is needed.

Because se is a clitic: a short, unstressed word that cannot just go anywhere.

In Croatian, clitics like se usually appear in special positions, and they do not normally go at the very end like useliti se when attached loosely after another verb in this kind of structure.

So:

• želi se useliti = natural and correct
• želi useliti se = unnatural / wrong

You may also hear or see:

• Naša nova podstanarka se želi useliti

That is also possible. Croatian clitic placement can be tricky, but želi useliti se is not the normal pattern.

Yes, there is a difference.

• seliti se = to move, to be in the process of moving house
• useliti se = to move in, to move into a new place

So useliti se focuses on the idea of entering and settling into the new home.

For example:

• Selimo se ovaj mjesec. = We are moving this month.
• Useljavamo se u novi stan. = We are moving into a new apartment.

In your sentence, useliti se is the more precise verb because it is specifically about moving into the place.

Here već means something like:

• already
• as early as
• as soon as

In this sentence, it adds the idea that next week is sooner than expected or surprisingly soon.

So:

• sljedeći tjedan = next week
• već sljedeći tjedan = already next week / as early as next week

It gives the sentence a sense of urgency or eagerness.

Because Croatian often uses the accusative without a preposition to express time when something happens.

So:

• sljedeći tjedan = next week
• prošli mjesec = last month
• ovu godinu = this year

This is a very common pattern.

English uses a preposition less visibly here too, but Croatian simply uses the time expression directly, with the appropriate case.

It is accusative singular.

Why? Because Croatian often uses the accusative of time for expressions like next week.

So:

• sljedeći tjedan = accusative singular
• tjedan happens to look the same as nominative here, because it is a masculine inanimate noun

For many masculine inanimate nouns, nominative and accusative singular have the same form.

Yes. Idući tjedan is also very common and natural.

Both usually mean:

• next week

Very roughly:

• sljedeći can feel a little more like following
• idući is also a standard everyday way to say next

In most normal contexts, they are interchangeable.

Croatian word order is fairly flexible, but the given order is natural.

The sentence:

• Naša nova podstanarka želi se useliti već sljedeći tjedan.

is a normal, neutral way to say it.

You could also move things for emphasis, for example:

• Već sljedeći tjedan naša nova podstanarka želi se useliti.
  This emphasizes already next week.

Or, if the subject is already known from context, Croatian can even omit it:

• Želi se useliti već sljedeći tjedan.

So the meaning stays similar, but the emphasis changes.