Bez potvrde ne mogu da primim paket danas.

Because bez always takes the genitive case in Serbian.

• potvrda = nominative singular, the basic dictionary form
• potvrde = genitive singular

So:

• bez potvrde = without a confirmation / without the document

This is a very common pattern:

• bez vode = without water
• bez novca = without money
• bez pasoša = without a passport

So if you see bez, you should usually expect the next noun to be in the genitive.

Potvrda can mean several related things depending on context:

• confirmation
• certificate
• receipt
• proof
• document showing approval or verification

In this sentence, it most likely means some required document or proof needed to receive the package, such as:

• a pickup confirmation
• a delivery slip
• an authorization document
• proof of identity/approval, depending on the situation

So even if the English translation gives one meaning, learners should know that potvrda is a flexible word in Serbian.

In Serbian, after verbs like moći (can, be able to), it is very common to use:

moći + da + present tense

So:

• mogu da primim = I can receive
• ne mogu da primim = I can’t receive

This is one of the most normal and natural structures in everyday Serbian.

You may also sometimes see an infinitive, especially in more formal style or in some regional usage:

• ne mogu primiti

But in modern spoken Serbian, ne mogu da primim is extremely common and often preferred.

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

• primati = imperfective, receiving / to be receiving / receive repeatedly
• primiti = perfective, to receive successfully, as a completed act

Here, primim comes from primiti. The idea is receiving the package as a single completed event.

So:

• ne mogu da primim paket danas = I can’t receive the package today

That sounds natural because receiving a package is usually seen as one complete action.

If you used primam, it would sound more like an ongoing or repeated process, which does not fit as well here.

Great question. In Serbian, perfective present often does not mean a true present ongoing action. Instead, it is often used:

• after da
• after modal verbs like mogu
• for future or completed-event meanings

So in ne mogu da primim, the form primim is grammatically present, but it refers to the possibility of a completed action.

You can think of it as:

• I cannot manage to receive it
• I am unable to receive it

This is completely normal in Serbian.

Paket is the direct object of primim, so it is in the accusative case.

For many masculine inanimate nouns in Serbian, the accusative singular looks exactly the same as the nominative singular.

So:

• nominative: paket
• accusative: paket

That is why there is no visible change.

Compare:

• Vidim paket. = I see the package.
• Primam paket. = I am receiving the package.

But with masculine animate nouns, accusative usually changes:

• student → studenta
• vidim studenta = I see the student

In Serbian, the negation particle ne is usually written separately from the verb:

• ne mogu = I cannot
• ne znam = I do not know
• ne idem = I am not going

So ne mogu is correct.

A learner may confuse this because a few forms are written as one word, such as:

• nemam = I do not have
• nisam = I am not
• neću = I will not

But with mogu, the correct form is:

• ne mogu

Yes. Serbian word order is fairly flexible, and moving danas is possible.

These are all possible:

• Bez potvrde ne mogu da primim paket danas.
• Bez potvrde danas ne mogu da primim paket.
• Danas ne mogu da primim paket bez potvrde.

The basic meaning stays similar, but the emphasis changes a little.

For example:

• Bez potvrde first gives strong emphasis to the missing document.
• danas earlier in the sentence emphasizes today more strongly.

So the original sentence is natural, but it is not the only possible word order.

No, danas can appear in different positions.

All of these are natural depending on emphasis:

• Danas ne mogu da primim paket bez potvrde.
• Ne mogu danas da primim paket bez potvrde.
• Bez potvrde ne mogu da primim paket danas.

Putting danas at the end can slightly highlight today, almost as if contrasting it with some other day:

• not today, maybe tomorrow

Serbian often uses word order to show focus rather than changing the basic grammar.

Yes, there can be a difference.

• primiti paket = to receive / accept the package
• dobiti paket = to get the package

In many situations they are close in meaning, but primiti often focuses more on the act of formally receiving or accepting something, especially in official or delivery contexts.

That makes primiti paket very natural here, especially if there is a required document.

Yes, depending on context, ne mogu can sometimes cover both ideas:

• I am unable to
• I am not allowed to
• it is not possible for me to

In this sentence, because of bez potvrde (without the confirmation/document), it may imply a rule or requirement:

• I can’t receive it because they won’t give it to me without that document

So the meaning may be practical, legal, or procedural rather than purely physical inability.

Yes, and in some contexts that may even sound more specific.

• primiti paket = receive the package
• preuzeti paket = pick up / collect the package

If you are talking about collecting a package from a post office, parcel locker, or courier office, preuzeti is often very natural.

So:

• Bez potvrde ne mogu da preuzmem paket danas.

would mean something like:

• Without the confirmation/document, I can’t pick up the package today.

The best choice depends on context, but both are good Serbian.