Odakle dolazi ona gusta magla iznad rijeke?

Odakle means from where or where ... from. It asks about origin.

• Odakle dolazi...? = Where does ... come from?
• Gdje je...? = Where is ...? (location)
• Kamo ide...? = Where is ... going? (direction toward a place)

So in this sentence, odakle is used because the question is about the source of the fog, not just its location.

Yes. Dolazi is the 3rd person singular present tense of dolaziti, which means to come or to be coming.

Here:

• dolazi = comes / is coming

Because the subject is magla (fog), which is singular, the verb is also singular:

• magla dolazi = the fog comes / is coming

In Croatian, present tense often covers both English simple present and present continuous, depending on context.

Because the subject is magla, and magla is singular.

Compare:

• magla dolazi = the fog comes
• oblaci dolaze = the clouds come

So dolazi agrees with a singular subject, while dolaze would be for a plural subject.

Here ona does not mean she. It is a demonstrative adjective/pronoun-like determiner meaning that.

So:

• ona gusta magla = that thick fog

Croatian uses forms like:

• ovaj / ova / ovo = this
• onaj / ona / ono = that

Because magla is a feminine noun, the form used here is ona.

Because magla is a feminine singular noun in the nominative case, and both the demonstrative (ona) and the adjective (gusta) must agree with it.

So all three match:

• ona = feminine singular nominative
• gusta = feminine singular nominative
• magla = feminine singular nominative

This kind of agreement is very important in Croatian.

Magla is in the nominative singular because it is the subject of the sentence.

The question is essentially:

• What comes from above the river?
• That thick fog comes.

So magla is the thing performing the action of the verb dolazi, which makes it the subject, and subjects are normally in the nominative.

Because iznad normally takes the genitive case.

• rijeka = nominative singular (river)
• rijeke = genitive singular (of the river / after certain prepositions)

So:

• iznad rijeke = above the river

This is something learners often need to memorize: many Croatian prepositions require a specific case, and iznad is one of the prepositions that usually goes with the genitive.

Iznad rijeke means above the river. It describes the location associated with the fog.

So:

• ona gusta magla iznad rijeke = that thick fog above the river

It tells you which fog the speaker means—the fog that is above the river.

Yes, Croatian word order is fairly flexible, though some orders sound more natural than others depending on emphasis.

The given sentence:

• Odakle dolazi ona gusta magla iznad rijeke?

A different but still possible version might be:

• Odakle ona gusta magla dolazi?

Or:

• Ona gusta magla iznad rijeke odakle dolazi?

These alternatives may sound more marked or emphasize different parts. The original sentence sounds natural and neutral.

Usually, yes. Gust often means thick, dense, or heavy, depending on context.

With magla (fog), natural English translations include:

• thick fog
• dense fog
• sometimes heavy fog

So gusta magla is a very normal Croatian phrase meaning thick/dense fog.

Rijeke is roughly pronounced ree-yeh-keh.

A few helpful points:

• r is rolled or tapped
• j sounds like English y
• ije is pronounced as a sequence, roughly ee-yeh

So:

• ri-je-ke

Learners often find ije tricky, but thinking of it as ee + yeh can help.

It uses the imperfective verb dolaziti.

• dolaziti = imperfective
• doći = perfective

In the present tense, Croatian normally uses imperfective verbs for ordinary present meaning:

• Magla dolazi. = The fog is coming / comes.

The perfective partner doći usually does not describe an ongoing present action in the same way. So dolazi is the expected choice here.

Yes, often it can. Odakle and otkud can both mean from where / where from.

So you may also hear:

• Otkud dolazi ona gusta magla iznad rijeke?

There can be small stylistic or regional preferences, but in many contexts they are very close in meaning. For a learner, it is useful to recognize both.