Žirafa je bila blizu ograde i polako je jela lišće.

This is the Croatian past tense normally called the perfect.

It is formed with:

• the auxiliary je from biti = to be
• plus a past participle, here bila and jela

So:

• je bila = was
• je jela = was eating / ate

In this sentence, the past tense describes the scene in the past.

Because there are two past-tense verb phrases:

• je bila = was
• je jela = was eating / ate

They are connected by i = and, but each verb phrase still has its own past-tense form.

So Croatian naturally says:

• Žirafa je bila... i polako je jela...

You may sometimes see the second auxiliary left out in coordinated sentences, but repeating je is completely normal and very common.

Because the subject žirafa is a feminine singular noun, and Croatian past participles agree with the grammatical gender and number of the subject.

So with žirafa:

• bila = feminine singular
• jela = feminine singular

Compare:

• masculine singular: bio, jeo
• feminine singular: bila, jela
• neuter singular: bilo, jelo

Even if you mean a male giraffe in real life, the noun žirafa is still grammatically feminine, so the verb form stays feminine.

Because blizu requires the genitive case.

The basic form is:

• ograda = fence

But after blizu:

• blizu ograde = near the fence

So ograde is the genitive singular form of ograda.

This is a very common pattern in Croatian:

• blizu kuće = near the house
• blizu škole = near the school
• blizu grada = near the city

In sentences like this, blizu works like a preposition-like word meaning near and it is followed by the genitive.

So:

• blizu ograde = near the fence

You may also hear blizu described as an adverb in some contexts, but for a learner the most useful thing is this:

When it is followed by a noun, that noun normally goes in the genitive.

Because lišće is a very common Croatian noun meaning leaves or foliage as a mass/collective idea.

Grammatically, lišće is neuter singular, but in meaning it refers to many leaves.

So:

• jela lišće = was eating leaves / foliage

If you wanted to emphasize individual leaves, you could use a form from list:

• list = leaf
• listovi = leaves
• listove = leaves, as a direct object

But in a sentence like this, lišće is the most natural choice.

Because Croatian does not have articles like English a and the.

So:

• žirafa can mean a giraffe or the giraffe
• ograde can mean of a fence or of the fence
• lišće can mean leaves or the leaves, depending on context

Croatian usually shows definiteness through:

• context
• word order
• demonstratives such as taj, ova, onaj when needed

Because je is a clitic, and Croatian clitics usually go in the second position of their clause.

In:

• i polako je jela lišće

the conjunction i does not count as the main first element, so polako is the first real stressed word, and je comes right after it.

That is why polako je jela sounds very natural.

Croatian word order is fairly flexible, but clitics like je strongly affect where things go.

Yes, Croatian word order is flexible enough that variants like that are possible.

But the word order changes the focus or rhythm a little.

Compare:

• polako je jela lišće = neutral, with polako placed prominently
• jela je polako lišće = also possible, with a slightly different flow

The version in your sentence is very natural because it highlights polako early and still keeps the clitic je in its usual position.

This is about aspect, which is very important in Croatian.

• jesti → jela is imperfective
• pojesti → pojela is perfective

Here, jela is used because the sentence describes an ongoing scene or activity:

• the giraffe was near the fence
• and it was slowly eating leaves

If you said pojela, it would suggest a completed action, more like:

• it ate up / finished eating the leaves

With polako and this descriptive scene, jela is the better choice.

A rough guide:

• žirafa ≈ ZHEE-ra-fa
  • ž sounds like the s in measure
• ograde ≈ O-gra-de
  • all vowels are pronounced clearly
• lišće is the trickiest, roughly LEESH-tye or LEESH-chye, depending on accent and how narrowly you imitate it
  • š sounds like sh
  • ć is a soft sound somewhat between t and ch
  • lj in words like lišće is not here, but in Croatian generally lj is a single sound, somewhat like the lli in million

A useful rule: Croatian spelling is much more regular than English spelling, so once you learn the special letters, pronunciation becomes much easier.