Film je bio dobar, ali večera nije bila jeftina.

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

So:

• film can mean a film or the film
• večera can mean a dinner, the dinner, or just dinner

The exact meaning depends on context. In this sentence, English would usually translate it as The film was good, but the dinner wasn't cheap or The movie was good, but dinner wasn't cheap.

Je is the 3rd person singular present form of biti (to be), and here it works as an auxiliary verb to form the past tense.

Serbian past tense is commonly built like this:

• auxiliary of biti
  • past participle

So:

• je bio = was for a masculine subject
• nije bila = was not for a feminine subject

In other words:

• Film je bio dobar = The film was good
• Večera nije bila jeftina = The dinner was not cheap

Because the past participle must agree with the gender and number of the subject.

Here:

• film is masculine singular → bio
• večera is feminine singular → bila

So the pattern is:

• masculine singular: bio
• feminine singular: bila
• neuter singular: bilo
• plural forms also change

This is a very important feature of Serbian grammar: verbs in the past tense show agreement with the subject.

For the same reason: adjectives also agree with the noun they describe.

• film is masculine singular, so: dobar
• večera is feminine singular, so: jeftina

So:

• dobar film = a good film
• jeftina večera = a cheap dinner

Even when the adjective comes after the verb, as in this sentence, it still agrees with the subject:

• Film je bio dobar
• Večera nije bila jeftina

In Serbian, the negative form of je is nije.

So:

• je = is / has / was as an auxiliary depending on context
• nije = is not / has not / was not

You do not normally say ne je in standard Serbian.

So:

• Večera nije bila jeftina = The dinner was not cheap

This is the normal and correct way to negate the past tense here.

Because je is a clitic, an unstressed word that usually goes in second position in the sentence or clause.

So Serbian prefers:

• Film je bio dobar

rather than:

• Film bio je dobar ✘

A useful beginner rule is:

• put the first main element first
• then put short clitic forms like je

So here:

• Film
  • je
    • bio dobar

Serbian word order is somewhat flexible, but clitics have special placement rules, and Film je bio dobar is the natural neutral order.

Usually, yes. Most Serbian nouns ending in -a are feminine.

So:

• večera is feminine
• that is why we get bila
• and also jeftina

Meanwhile:

• film is masculine
• so we get bio
• and dobar

This is a very common pattern, though there are some exceptions in the language.

They are both in the nominative case because they are the subjects of their clauses.

• Film je bio dobar
• večera nije bila jeftina

In Serbian, the subject is normally in the nominative, just as in English we use he, she, the film, the dinner as subjects.

So there is no case change here because both nouns are simply the things being talked about.

Yes, ali means but.

It introduces a contrast:

• Film je bio dobar = positive statement
• ali večera nije bila jeftina = contrasting statement

Serbian also has a, which can sometimes mean and/but depending on context, but ali is the clearer, stronger choice for a direct contrast like this one.

So in this sentence, ali is exactly what you would expect.

Yes, but the meaning changes.

• Film je dobar = The film is good / The film is a good one
• Film je bio dobar = The film was good

So:

• je dobar = present
• je bio dobar = past

The word bio is what makes it past tense together with the auxiliary structure.

A few useful pronunciation notes:

• j is pronounced like English y in yes
  • so je sounds roughly like ye
  • jeftina begins with a y sound: yef-
• č is like ch in church, but usually a bit firmer
  • so večera is roughly VE-che-ra
• Serbian spelling is very phonetic, so words are usually pronounced the way they are written

Very rough approximations:

• Film je bio dobar ≈ Feelm ye bee-oh doh-bar
• večera nije bila jeftina ≈ VE-che-ra NEE-ye BEE-la YEF-tee-na

These are only approximations, but they help at the beginning.