Što više slušam hrvatski, to mi zvuk jezika postaje prirodniji.

In this structure, što does not mean “what”; it is part of a fixed comparative pattern:

• Što više… to… = The more… the more…

So:

• Što više slušam hrvatski… = The more I listen to Croatian…

You’ll see it a lot with comparatives:

• Što više učiš, to više znaš. – The more you study, the more you know.

Here što is best thought of as “the” in “the more…”, not as “what”.

Here to is the second half of the same correlative structure:

• Što više… to… = The more… the more…

So to is like the second “the” in English:

• Što više slušam hrvatski, to mi zvuk jezika postaje prirodniji.
  = The more I listen to Croatian, the more natural the sound of the language becomes to me.

It doesn’t mean “that” or “it” here; it’s just a grammatical word tying the two halves of the comparison together.

Mi is the unstressed dative pronoun meaning “to me / for me.”

• to mi zvuk jezika postaje prirodniji
  literally: then to-me the-sound of-the-language becomes more-natural

It marks the “experiencer”: the sound is becoming more natural to me.

As for position: Croatian clitic pronouns like mi, ti, mu, joj usually stand in second position in the clause (after the first stressed word or phrase). Here the first element is to, so mi comes right after it: to mi…

Hrvatski here is the direct object of the verb slušati (to listen to). Direct objects are in the accusative case.

For masculine singular adjectives/nouns in the inanimate sense (like languages), the nominative and accusative look the same:

• Nominative: hrvatski (Croatian – as a language/adjective)
• Accusative (inanimate): hrvatski

So slušam hrvatski = “I listen to Croatian.”
Hrvatskog would be the genitive (or animate accusative), not correct here.

You can absolutely say slušam hrvatski jezik; it’s correct and clear.

• slušam hrvatski – perfectly natural, common (the word “language” is understood)
• slušam hrvatski jezik – a bit more explicit, sometimes slightly more formal or emphatic

Both mean “I listen to Croatian (language).”

Zvuk jezika is a “X of Y” construction: the sound of the language.

In Croatian, the “of” relationship is usually shown with the genitive case:

• zvuk – nominative (subject)
• jezika – genitive singular of jezik (language)

So:

• zvuk jezika = “the sound of the language”

Zvuk jezik would just be two nominatives together (incorrect here), and zvuk jeziku uses the dative, which doesn’t express this “of” relation.

Postaje is the third person singular present of postajati – “to become.”

• zvuk jezika je prirodan – “the sound of the language is natural”
• zvuk jezika postaje prirodniji – “the sound of the language is becoming more natural”

So postajati expresses a change of state over time, not a static description. In this sentence, it highlights the gradual process: as you listen more, the sound slowly becomes more natural.

The base adjective is prirodan (natural). The comparative is made by:

1. Dropping the final -an: prirod-
2. Adding -niji (or just -iji depending on the stem): prirodniji

So:

• prirodan – natural
• prirodniji – more natural

You could also use the adverbial form:

• prirodno – naturally / in a natural way
• prirodnije – more naturally

But in this sentence, we’re comparing the adjective (the sound is more natural), so prirodniji is used.

Yes, that word order is also correct:

• Što više slušam hrvatski, to prirodniji mi zvuk jezika postaje.

Croatian word order is relatively flexible. You can move elements around to change emphasis, as long as clitics (like mi) stay in their usual positions (second in the clause).

Your version puts more emphasis on prirodniji by placing it earlier in the clause; the meaning remains the same.

You can say:

• Što više slušam hrvatski, zvuk jezika mi postaje prirodniji.

It’s grammatical and understandable. However, you then lose the neat, symmetrical što… to… structure.

With to, the style is more idiomatic and clearly expresses: “the more X, the more Y.” Without to, it feels slightly less like a fixed comparative pattern and more like a simple “as X increases, Y happens.” Both are fine, but što… to… is very typical.

Slušam is present tense, but here it expresses a general, ongoing habit or tendency, not just “right now at this moment.”

This is similar to English:

• “The more I listen to Croatian, the more natural it becomes to me.” (present simple, general truth)

If you wanted to talk about a completed past period, you could say:

• Što sam više slušao hrvatski, to mi je zvuk jezika postajao prirodniji.
  – The more I listened to Croatian (in the past), the more natural the sound became to me.

In the given sentence, the present tense underlines a general learning process that’s still relevant now.

• Slušam = I listen (actively)
  You choose to pay attention to the sounds.

• Čujem = I hear (passively)
  Your ears register the sound; it may or may not be intentional.

In this sentence, the focus is on purposeful listening as part of learning, so slušam hrvatski is the natural choice.
Čujem hrvatski would just mean “I hear Croatian (around me).”