Pošiljka je napolju pored vrata.

Pošiljka usually means shipment, delivery, parcel, or package, depending on context.

In everyday speech, if someone is talking about something that has arrived or is being delivered, English will often use package or parcel.
So in this sentence, pošiljka is most naturally understood as the package / the delivery.

It is a feminine noun, which is why it matches je as a singular subject.

Je is the 3rd person singular present form of biti (to be), so it means is.

So:

• Pošiljka = the package / shipment
• je = is
• napolju = outside
• pored vrata = by the door / next to the door

Together: The package is outside by the door.

In Serbian, subject pronouns are often left out when they are not needed.

English says:

• It is outside.

But Serbian usually just says:

• Napolju je. or Pošiljka je napolju.

Since the noun pošiljka is already stated, there is no need to add a separate pronoun.

Napolju means outside or outdoors.

In this sentence, it tells you the package is not inside.
So napolju pored vrata means something like:

• outside by the door
• outside next to the door

A learner may also see vani in some varieties of Serbian/Croatian/Bosnian. Napolju is a very common Serbian form.

Pored means beside, next to, or by.

So:

• pored vrata = by the door / next to the door

It gives the location more precisely.
Without it, Pošiljka je napolju would just mean The package is outside.
With pored vrata, you know where outside: by the door.

Because pored requires the genitive case.

So the noun after pored must be in the genitive:

• pored + genitive

The tricky part is that vrata is a special noun. It is a plural-only noun in Serbian, even when it means one door in English. Its genitive plural form is also vrata, so the form looks unchanged here.

That is why you get:

• pored vrata = beside the door

Because vrata is one of those Serbian nouns that are grammatically plural even when they refer to one object.

So although English has:

• door (singular)

Serbian normally uses:

• vrata (grammatically plural)

This is just something learners have to get used to. Other Slavic languages do similar things with certain objects.

For example:

• Vrata su otvorena. = The door is open.

Notice that Serbian uses plural agreement there: su otvorena, not singular.

The given order is natural:

• Pošiljka je napolju pored vrata.

Serbian word order is fairly flexible, but changing it can shift emphasis.

For example:

• Pošiljka je napolju pored vrata. = neutral
• Napolju je pošiljka, pored vrata. = more marked, emphasizing outside
• Pošiljka je pored vrata napolju. = possible, but less natural in many contexts

So the original sentence is a good standard way to say it.

Serbian does not have articles like English a / an / the.

So:

• pošiljka can mean a package or the package
• vrata can mean a door / the door, depending on context

Context tells you whether the meaning is definite or indefinite.

In this sentence, English will often translate it as the package is outside by the door, because the situation usually makes it clear which package and which door are meant.

Yes, often you could, but the meaning shifts slightly.

• paket = package / parcel as a physical object
• pošiljka = shipment / delivery / package sent, a bit broader

So:

• Paket je napolju pored vrata. = The package is outside by the door.
• Pošiljka je napolju pored vrata. = similar, but can sound a little more like the delivery/shipment

In everyday conversation, paket is often the more concrete and common word if you mean a box or parcel sitting there physically.

It is not redundant.

• pored vrata tells you where relative to the door
• napolju tells you inside or outside

So pored vrata alone could mean:

• by the door inside
• by the door outside

But napolju pored vrata clearly means:

• outside, by the door

That extra word gives important information.

A simple approximate pronunciation is:

• Pošiljka ≈ PO-sheel-yka
• je ≈ yeh
• napolju ≈ na-PO-lyu
• pored ≈ PO-red
• vrata ≈ VRA-ta

A few useful sound notes:

• š sounds like sh
• j sounds like English y
• lj is a soft sound, roughly like ly in million, though not exactly the same

So the whole sentence is roughly:

PO-sheel-yka yeh na-PO-lyu PO-red VRA-ta