Moja sestra radi blizu trga, a moja prijateljica živi blizu reke.

Because moja is the feminine singular form of moj (my). Both sestra and prijateljica are feminine singular nouns, so the possessive adjective has to agree with them.

• moj brat = my brother
• moja sestra = my sister
• moje dete = my child

So here moja matches both feminine nouns.

Because blizu normally takes the genitive case.

The basic forms are:

• trg = square
• reka = river

But after blizu they change to genitive:

• blizu trga = near the square / near a square
• blizu reke = near the river / near a river

So the case change is caused by blizu.

Here a connects two clauses, but it is not exactly the same as i.

• i = plain and
• a = and, but often with a slight contrast, comparison, or topic shift

So in this sentence, a sounds natural because it sets the two statements side by side:

• My sister works near the square, and my friend lives near the river.

It is not a strong contrast like but, but it does feel a little more like while/as for than simple and.

They are in the nominative case because they are the subjects of the verbs.

• Moja sestra radi = my sister works
• Moja prijateljica živi = my female friend lives

So the sentence has:

• nominative subjects: moja sestra, moja prijateljica
• genitive after blizu: trga, reke

Because Serbian often does not need subject pronouns when the subject is already clear.

In this sentence, the subjects are stated directly:

• moja sestra
• moja prijateljica

So there is no need to add ona (she). Serbian usually avoids extra subject pronouns unless they are needed for emphasis or contrast.

It is repeated because each noun phrase has its own possessive adjective:

• moja sestra
• moja prijateljica

This is normal and clear. If you remove the second moja, the meaning may become less specific or slightly different in feel. Repeating it makes it clear that both are my sister and my friend.

So the repetition is natural, not awkward.

No. Serbian does not have articles like English a and the.

That means:

• blizu trga can mean near the square or near a square
• blizu reke can mean near the river or near a river

The exact meaning depends on context. English has to choose a or the, but Serbian usually leaves that unstated.

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

So:

• blizu trga
• blizu reke

You can think of it as functioning very much like a preposition for learning purposes. The important practical rule is: blizu + genitive.

Usually they are understood as general present-time facts here:

• radi = works
• živi = lives

So the sentence most naturally means:

• My sister works near the square
• My friend lives near the river

Serbian present tense can sometimes also refer to what is happening now, but with verbs like raditi and živeti/živjeti, the usual reading in a sentence like this is general or habitual.

Yes. Serbian word order is more flexible than English word order, because case endings help show each word’s role.

For example, you could also say:

• Moja sestra radi blizu trga, a moja prijateljica živi blizu reke.
• Blizu trga moja sestra radi, a blizu reke moja prijateljica živi.

But the original version is the most neutral and natural for a learner. Changing the order usually changes emphasis, not the basic meaning.

A few useful pronunciation points:

• ž sounds like the s in measure
• j sounds like English y
• lj is a soft ly-like sound
• c sounds like ts

So roughly:

• živi ≈ ZHEE-vee
• moja ≈ MO-ya
• prijateljica ≈ pree-ya-TEL-yee-tsa

These are only rough English approximations, but they can help you get started.