Gostujuća mreža radi.

Because it agrees with mreža, which is a feminine singular noun in the nominative case.

In Croatian, adjectives change their endings to match the noun they describe in:

• gender
• number
• case

So here:

• mreža = feminine singular nominative
• gostujuća also becomes feminine singular nominative

The dictionary form is gostujući, and here it changes to gostujuća to match mreža.

Mreža is feminine.

A very common clue is that many Croatian nouns ending in -a are feminine. That is not true 100% of the time, but it is a strong general pattern.

So in this sentence:

• mreža = feminine noun
• that is why the adjective is gostujuća, not gostujući or gostujuće

Because the subject is singular.

• mreža = one network
• so the verb must be 3rd person singular
• raditi → radi

If the subject were plural, you would use rade:

• Gostujuće mreže rade. = Guest networks work / are working.

It can mean both, depending on context.

Croatian does not have a separate continuous form like English is working. The present tense radi can cover:

• works
• is working
• is functioning
• is running

So Gostujuća mreža radi. can mean:

• the guest network works
• the guest network is working
• the guest network is functioning

Because Croatian has no articles.

English uses:

• a
• an
• the

Croatian normally does not use separate words for those. Whether something is understood as a network or the network depends on context.

So Gostujuća mreža radi. can naturally be understood as The guest network works if the listener already knows which network is meant.

Yes. Here radi is the present tense of raditi.

With people, raditi often means to work:

• On radi. = He is working.

With machines, devices, systems, or networks, it often means:

• to work
• to function
• to be operational

So in this sentence, radi means the network is functioning properly.

Yes, it is understandable and natural, especially in technical or interface-style language.

You may also hear:

• mreža za goste = literally network for guests

Both can be used, but they feel slightly different:

• gostujuća mreža sounds a bit more compact and label-like
• mreža za goste is very transparent and everyday

In menus, settings, and technical contexts, both are possible.

Yes, Croatian word order is more flexible than English, but not all orders sound equally neutral.

The most neutral order here is:

• Gostujuća mreža radi.

You could also say:

• Radi gostujuća mreža.

But that would usually add emphasis, roughly like:

• The guest network is working
• or It’s the guest network that works

So for a simple neutral statement, Gostujuća mreža radi is the best choice.

A rough guide:

• gostujuća ≈ gos-too-yoo-cha
• mreža ≈ mreh-zha
• radi ≈ rah-dee

A few useful sound notes:

• ž sounds like the s in measure
• ć is a soft sound, somewhat like a softer ch/ty
• j is pronounced like English y

So gostujuća mreža radi sounds roughly like:

gos-too-YOO-cha MREH-zha RAH-dee