Narod želi bržu mrežu.

Because mreža is the direct object of želi.

In Croatian, direct objects usually go in the accusative case.
Mreža is a feminine noun, and feminine singular nouns ending in -a normally change that ending to -u in the accusative:

• mreža = nominative
• mrežu = accusative

So želi mrežu means wants a network or wants the network, depending on context.

Because the adjective has to match the noun it describes in gender, number, and case.

The noun mrežu is:

• feminine
• singular
• accusative

So the adjective must also be feminine singular accusative.

Here the adjective is the comparative form of brz:

• brz = fast
• brži = faster

With a feminine singular noun:

• nominative: brža mreža
• accusative: bržu mrežu

So bržu mrežu is the correct form for a faster network as the object of the verb.

Želi is the 3rd person singular present tense of the verb željeti, which means to want.

A few present-tense forms are:

• želim = I want
• želiš = you want
• želi = he/she/it wants
• želimo = we want
• želite = you all / formal you want
• žele = they want

Since the subject here is narod, which is grammatically singular, the sentence uses želi.

Because narod is a grammatically singular collective noun.

Even though it refers to a group of people, Croatian treats narod as singular, so the verb is singular too:

• Narod želi... = correct
• Narod žele... = incorrect in standard Croatian

This is similar to how English sometimes uses singular collective nouns like the government wants.

Narod is in the nominative singular, because it is the subject of the sentence.

So the basic structure is:

• Narod = subject, nominative
• želi = verb
• bržu mrežu = direct object, accusative

Yes. Bržu comes from the comparative adjective brži, meaning faster.

Here is the basic comparison:

• brz / brza / brzo = fast
• brži / brža / brže = faster
• najbrži / najbrža / najbrže = fastest

Because the noun is mrežu in the accusative, the comparative feminine form changes to bržu.

So you can compare:

• brza mreža = a fast network
• brža mreža = a faster network
• bržu mrežu = a faster network, as an object
• najbrža mreža = the fastest network

Croatian does not have articles like English the and a/an.

So a sentence like Narod želi bržu mrežu can be translated into natural English with an article, even though Croatian does not say one explicitly.

Which article you choose in English depends on context:

• a faster network
• the faster network

In most ordinary contexts, this sentence would naturally be understood as a faster network.

Yes. Croatian word order is more flexible than English because case endings show what each word is doing.

The neutral, straightforward order is:

• Narod želi bržu mrežu.

But other orders are possible for emphasis, for example:

• Bržu mrežu narod želi.
• Narod bržu mrežu želi.

These versions still mean basically the same thing, but the emphasis changes. For learners, the original order is the best neutral pattern to remember.

Both can relate to people, but they are not used in exactly the same way.

• narod = the people, the nation, the populace; often a collective or societal group
• ljudi = people, persons, human beings; the ordinary plural of čovjek in everyday use

So narod želi bržu mrežu sounds like the people as a whole want a faster network.

If you said Ljudi žele bržu mrežu, that would mean People want a faster network, with a more general everyday sense. Notice that ljudi is plural, so the verb becomes žele.

The letter ž is pronounced like the sound in English measure or vision.

So roughly:

• želi ≈ ZHE-lee
• bržu ≈ BR-zhu
• mrežu ≈ MRE-zhu

And the whole sentence can be approximated as:

• NA-rod ZHE-lee BR-zhu MRE-zhu

That is only an approximation for English speakers, but it is a good start.

Željeti is the standard verb for to want, and it works very naturally with a noun phrase object like bržu mrežu.

• Narod želi bržu mrežu. = natural and standard

Croatian also has htjeti with the form hoće, which can mean want or help express the future, but it behaves a bit differently and often has a slightly different feel.

For a simple sentence meaning wants a faster network, želi is the clearest and most standard choice.