Ta bajka je zanimljiva; zmaj u njoj pomaže maloj djevojčici.

Ta means that and points to a specific fairy tale already known from context.

• bajka = fairy tale
• ta bajka = that fairy tale

Like adjectives, Croatian demonstratives agree with the noun in gender, number, and case. Since bajka is feminine singular nominative, the form is ta.

You could also say just Bajka je zanimljiva if you mean The fairy tale is interesting in a more general or less pointed way.

Because it agrees with bajka, which is a feminine singular noun.

• bajka = feminine singular
• zanimljiv = interesting
• feminine singular form = zanimljiva

So:

• Ta bajka je zanimljiva. = That fairy tale is interesting.

Even though zanimljiva comes after je, it still matches the noun it describes.

Bajka is in the nominative singular because it is the subject of the first clause:

• Ta bajka je zanimljiva.

The thing that is interesting is bajka, so it stays in the nominative.

Njoj here means it/her, referring back to bajka.

The phrase u njoj means in it.

Why njoj?

• the preposition u can require the locative when it means location
• njoj is the locative singular form of the pronoun referring to a feminine noun

So:

• u bajci = in the fairy tale
• u njoj = in it

Since bajka is feminine, the pronoun is feminine too.

Because u njoj expresses location, not movement.

Croatian often makes this distinction:

• u + locative = in, inside somewhere
• u + accusative = into somewhere

So:

• zmaj je u njoj = the dragon is in it
• zmaj ulazi u nju = the dragon goes into it

In your sentence, the dragon is acting inside the story, so u njoj is correct.

Zmaj is in the nominative singular because it is the subject of the second clause:

• zmaj u njoj pomaže maloj djevojčici

The dragon is the one doing the action of helping, so zmaj stays in the nominative.

Because the verb pomagati / pomoći takes the dative, not the accusative.

In Croatian, you help to someone, grammatically speaking. So the person receiving the help goes in the dative.

• djevojčica = nominative
• djevojčici = dative

And the adjective must match:

• mala djevojčica = nominative
• maloj djevojčici = dative

So:

• pomaže maloj djevojčici = helps the little girl

This is a very important verb pattern to remember.

Pomaže is the 3rd person singular present tense form of pomagati.

It means:

• he helps
• she helps
• it helps

In this sentence, the subject is zmaj, so:

• zmaj pomaže = the dragon helps

Croatian verbs usually do not need a separate subject pronoun like he or it, because the verb form already shows the person and number.

Croatian often uses the present tense when talking about what happens in the plot of a story, book, film, or fairy tale.

So:

• zmaj u njoj pomaže maloj djevojčici

can naturally mean:

• the dragon helps a little girl in it
• or, in smoother English, in it, a dragon helps a little girl

This is similar to the literary present in English, as in In the story, the hero defeats the monster.

It is dative singular feminine.

Both words show the dative:

• mala → maloj
• djevojčica → djevojčici

They must agree because maloj describes djevojčici.

This whole phrase is in the dative because it is the object of pomaže.

Djevojčica does contain a diminutive-looking ending, but in normal modern usage it simply means girl, usually a young girl.

So:

• djevojka = girl/young woman
• djevojčica = little girl / young girl

In your sentence, the adjective mala already adds the idea of small/little, so:

• mala djevojčica = a little girl

It sounds natural, not redundant.

Yes. Croatian word order is more flexible than English word order, though some versions sound more neutral than others.

The original sentence:

• Ta bajka je zanimljiva; zmaj u njoj pomaže maloj djevojčici.

is natural and clear.

You could also say:

• Ta bajka je zanimljiva; u njoj zmaj pomaže maloj djevojčici.

This puts a bit more focus on u njoj = in it.

Croatian often moves parts of the sentence around for focus, rhythm, or style, while the case endings keep the meaning clear.

The semicolon links two closely related complete clauses:

• Ta bajka je zanimljiva
• zmaj u njoj pomaže maloj djevojčici

It shows that the second clause explains or develops the first one. In English, a semicolon works similarly.

A full stop would also be possible:

• Ta bajka je zanimljiva. Zmaj u njoj pomaže maloj djevojčici.

A comma would usually be weaker and less standard here.

Yes. That would also be correct:

• Zmaj u bajci pomaže maloj djevojčici.

This means exactly The dragon helps a little girl in the fairy tale.

Using u njoj avoids repeating bajka and sounds more natural in connected speech.

Bajka usually means fairy tale, often with magical or fantastical elements.

Priča is more general and means story.

So:

• bajka = fairy tale
• priča = story

Because the sentence contains zmaj and a djevojčica, bajka fits very naturally.