Posle večere slušamo lepu pesmu.

Because posle requires the genitive case.

The basic form is večera.
After the preposition posle (after), it changes to genitive singular:

• nominative: večera
• genitive: večere

So posle večere means after dinner.

A very useful rule to remember is:

• posle + genitive

Examples:

• posle škole = after school
• posle ručka = after lunch
• posle večere = after dinner

Because pesmu is the direct object of the verb slušamo, so it must be in the accusative case.

The dictionary/basic form is:

• lepa pesma = nominative singular

But after a verb like slušati (to listen to), the thing being listened to goes into the accusative:

• nominative: lepa pesma
• accusative: lepu pesmu

Both the adjective and the noun change, because adjectives in Serbian must agree with the noun in gender, number, and case.

So:

• lepa → lepu
• pesma → pesmu

Because Serbian often drops subject pronouns when the verb ending already makes the subject clear.

The verb slušamo means we listen or we are listening.
The ending -mo tells you the subject is we.

So Serbian usually says:

• Slušamo lepu pesmu.

instead of

• Mi slušamo lepu pesmu.

You can add mi if you want emphasis or contrast, such as:

• Mi slušamo lepu pesmu, a oni gledaju film.
  We are listening to a nice song, and they are watching a movie.

Slušamo is the 1st person plural present tense form of slušati.

Breakdown:

• infinitive: slušati = to listen
• present stem: sluša-
• ending: -mo = we

So slušamo means:

• we listen
• we are listening

Which English translation fits best depends on context.

It can mean either one. Serbian present tense often covers both meanings that English separates.

So slušamo can mean:

• we listen = habitual action
• we are listening = action happening now

Context decides.

With posle večere, many learners feel it sounds slightly natural as a repeated or usual action, like After dinner, we listen to a nice song, but it can also describe what is happening at a particular moment.

This is a very common difference between English and Serbian.

In English:

• listen to a song

In Serbian:

• slušati pesmu

So Serbian does not need a word like to here. The verb slušati takes a direct object in the accusative case.

More examples:

• slušam muziku = I listen to music
• sluša radio = he/she listens to the radio
• slušamo pesmu = we listen to a song

Yes. Serbian word order is more flexible than English word order because case endings show grammatical roles.

The given sentence is a very normal, neutral way to say it:

• Posle večere slušamo lepu pesmu.

But you could also hear:

• Slušamo lepu pesmu posle večere.
• Lepu pesmu slušamo posle večere.

These versions are not exactly identical in emphasis:

• putting posle večere first can frame the time first
• putting lepu pesmu earlier can emphasize the object

So the word order can change, but the original sentence sounds natural and neutral.

Not always. Pesma can mean song, and in some contexts it can also mean poem.

But in this sentence, because the verb is slušamo (we listen to), pesma is understood as song, not poem.

Compare:

• slušamo pesmu = we listen to a song
• čitamo pesmu = we read a poem

So the verb often tells you which meaning is intended.

Because Serbian has no articles.

English distinguishes:

• a song
• the song

Serbian usually just says:

• pesma / pesmu

The exact meaning depends on context.

So lepu pesmu could mean:

• a nice song
• the nice song

In many learning materials, a nice song is the most natural default translation, but Serbian itself does not mark that difference with an article.

No. Another common word is nakon.

So you could also say:

• Nakon večere slušamo lepu pesmu.

Both posle and nakon mean after and both take the genitive case.

Very roughly:

• posle often sounds a bit more everyday and conversational
• nakon can sound a bit more formal or bookish in some contexts

But both are correct.

The main tricky letters here are:

• š = sh as in shoe
• č = a ch sound, roughly like church

So:

• slušamo ≈ SLOO-sha-mo
• večere ≈ VE-che-re

A rough full pronunciation guide:

• Posle ≈ POS-le
• večere ≈ VE-che-re
• slušamo ≈ SLOO-sha-mo
• lepu ≈ LE-pu
• pesmu ≈ PES-mu

Also, Serbian spelling is very phonetic, so words are usually pronounced much the way they are written.

Here is the full breakdown:

• Posle — preposition
• večere — genitive singular of večera, because posle takes genitive
• slušamo — verb, 1st person plural present
• lepu — adjective, accusative singular feminine
• pesmu — noun, accusative singular feminine

So the structure is:

• time phrase: posle večere
• verb: slušamo
• direct object: lepu pesmu

That is why the sentence looks the way it does grammatically.