Ako mi profesorica sutra vrati zadaću, pregledat ću svaki ispravak što pažljivije.

In Croatian, after ako (if), you normally use the present tense even when the meaning is future.

So:

• Ako mi profesorica sutra vrati zadaću...
  literally looks like If the teacher returns the homework to me tomorrow...
• but in natural English it means If my teacher returns my homework tomorrow...

This is very similar to English in sentences like:

• If she comes tomorrow, I’ll talk to her.

English also uses a present form (comes) after if, even though the situation is in the future.

Also, vratiti is a perfective verb, and perfective present forms often refer to a future completed action in contexts like this.

Mi is the unstressed dative form of ja (I / me), so here it means to me.

• Ako mi profesorica vrati zadaću... = If the teacher returns the homework to me...

Croatian often uses a dative pronoun where English might prefer a possessive:

• vrati mi zadaću = returns my homework to me / gives my homework back to me

So mi is not the subject. The subject is profesorica.

Because zadaću is the accusative singular form of zadaća.

• nominative: zadaća = homework
• accusative: zadaću

It is in the accusative because it is the direct object of vrati:

• profesorica vrati zadaću = the teacher returns the homework

This is a very common pattern with feminine nouns ending in -a:

• knjiga → knjigu
• bilježnica → bilježnicu
• zadaća → zadaću

Both refer to the future, but pregledat ću is the normal written and spoken contracted form.

Croatian future I is formed with:

• infinitive + clitic form of htjeti

With many verbs, when the infinitive ends in -ti, the final -i is dropped before ću:

• pregledati + ću → pregledat ću
• gledati + ću → gledat ću
• čitati + ću → čitat ću

So pregledat ću means I will review/look over.

You may also see the auxiliary first:

• Ću pregledati... is not correct at the beginning of a sentence.
• Correct: Pregledat ću...
• Also correct in some contexts: Ja ću pregledati...

Because ću is a clitic—a short unstressed word that usually takes the second position in its clause.

In the future tense, Croatian often writes the lexical verb and the auxiliary separately:

• pregledat ću
• napisat ću
• vidjet ću

So although English says I will review, Croatian literally has something like review will-I.

This is normal and one of the first things learners notice about Croatian word order.

Svaki ispravak means every correction.

It is singular because svaki works like English every, which also normally takes a singular noun:

• every correction
• not every corrections

So:

• pregledat ću svaki ispravak = I’ll look over every correction

If you wanted all corrections, you would use a plural expression instead, such as:

• sve ispravke

That changes the nuance slightly:

• svaki ispravak = each individual correction, one by one
• sve ispravke = all the corrections as a whole

Because ispravak is a masculine inanimate noun, and for many masculine inanimate nouns, the nominative and accusative singular are identical.

So:

• nominative: ispravak
• accusative: ispravak

That is why it does not visibly change after pregledat ću.

Compare:

• vidim stol = I see the table
• stol looks the same in nominative and accusative

But with masculine animate nouns, accusative usually changes:

• profesor → profesora

Što pažljivije means as carefully as possible or as carefully as I can.

This is a common Croatian pattern:

• što + comparative

Here:

• pažljivo = carefully
• pažljivije = more carefully
• što pažljivije = as carefully as possible

You can think of it as meaning:

• in the most careful way possible

Similar examples:

• što brže = as quickly as possible
• što bolje = as well as possible
• što jasnije = as clearly as possible

Because after što in this pattern, Croatian uses the comparative form, not the basic adverb.

So:

• pažljivo = carefully
• pažljivije = more carefully

Then:

• što pažljivije = as carefully as possible

This may feel unusual to an English speaker, because English does not literally say as more carefully as possible, but Croatian does use the comparative here.

Because the sentence begins with a subordinate if-clause:

• Ako mi profesorica sutra vrati zadaću, ...

After that clause, Croatian places a comma before the main clause:

• ..., pregledat ću svaki ispravak što pažljivije.

This is the same logic as in English:

• If my teacher returns my homework tomorrow, I’ll review every correction as carefully as possible.

So the comma marks the boundary between:

1. the condition
2. the main result/action

Yes, Croatian word order is fairly flexible, although some positions are more natural than others.

The original sentence is very natural:

• Ako mi profesorica sutra vrati zadaću, pregledat ću svaki ispravak što pažljivije.

Possible variations include:

• Ako profesorica sutra vrati mi zadaću... — this is much less natural because clitics like mi normally come early
• Ako sutra mi profesorica vrati zadaću... — possible, but less standard/natural
• Sutra ću pregledati svaki ispravak što pažljivije, ako mi profesorica vrati zadaću. — possible, with a slightly different emphasis

The main thing to remember is that clitics such as mi and ću tend to appear in second position in their clause.

Because Croatian often expresses possession with a dative pronoun instead of a possessive adjective when the meaning is obvious.

So:

• profesorica mi vrati zadaću literally = the teacher returns the homework to me
• but in natural English this is often just the teacher returns my homework

Croatian can also say:

• moju zadaću

But that would be more explicit or emphatic:

• Ako mi profesorica sutra vrati moju zadaću...

Usually, mi already makes the ownership clear enough.

Yes. Vratiti is a perfective verb, and that matters.

In Croatian, aspect is very important:

• vraćati = imperfective, ongoing/repeated returning
• vratiti = perfective, a completed act of returning

Here the sentence refers to one completed future event:

• If the teacher gives my homework back tomorrow...

That is why vrati (from perfective vratiti) is the natural choice.

Using the imperfective vraća here would usually sound wrong or at least unnatural for this specific meaning.

Yes. Profesorica is the feminine form, meaning female teacher / professor depending on context.

• profesorica = female teacher/professor
• profesor = male teacher/professor

So if the teacher were male, you would say:

• Ako mi profesor sutra vrati zadaću, pregledat ću svaki ispravak što pažljivije.

In many school contexts, profesor/profesorica can mean teacher, not only university professor.

Not exactly. They are similar, but not identical.

• vrlo pažljivo = very carefully
• što pažljivije = as carefully as possible

So:

• Pregledat ću svaki ispravak vrlo pažljivo.
  = I’ll review every correction very carefully.

• Pregledat ću svaki ispravak što pažljivije.
  = I’ll review every correction as carefully as possible.

The second one sounds stronger and more goal-oriented. It suggests making the maximum effort.

Because Croatian often omits subject pronouns when the verb ending already shows who the subject is.

• pregledat ću already means I will review

So ja is unnecessary unless you want emphasis or contrast:

• Ja ću pregledati svaki ispravak...
  = I will review every correction...

That might imply contrast, for example:

• Ja ću pregledati svaki ispravak, a on neće.
  = I will review every correction, but he won’t.

In the original sentence, no emphasis is needed, so the pronoun is left out.