Ja ponekad učim jezik na računaru.

You can usually leave it out.

Serbian often drops subject pronouns when the verb already makes the subject clear. Since učim means I learn / I am learning, the ja is not necessary.

So both are possible:

• Ja ponekad učim jezik na računaru.
• Ponekad učim jezik na računaru.

Including ja can add emphasis, contrast, or clarity. For example, it may sound like I sometimes learn a language on the computer, as opposed to someone else.

Ponekad means sometimes.

It is an adverb of frequency, and Serbian word order is fairly flexible, so it can appear in different places:

• Ja ponekad učim jezik na računaru.
• Ponekad učim jezik na računaru.
• Ja učim jezik ponekad na računaru.

The first two are more natural.

In everyday Serbian, adverbs like ponekad, često (often), uvek (always), and retko (rarely) commonly appear near the beginning of the sentence or before the verb.

Učim is the 1st person singular present tense form of the verb učiti.

So:

• učim = I learn / I am learning
• učiš = you learn
• uči = he/she learns
• učimo = we learn
• učite = you (plural/formal) learn
• uče = they learn

In Serbian, the present tense can often translate into English in more than one way depending on context:

• I learn
• I am learning
• sometimes even I study

It is the object, but for this noun the form happens to stay the same.

Jezik is a masculine inanimate noun. In Serbian, masculine inanimate nouns usually have the same form in the nominative and accusative singular.

So:

• nominative: jezik
• accusative: jezik

That is why after učim you still see jezik.

Compare that with a masculine animate noun, where accusative usually changes:

• nominative: student
• accusative: studenta

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

So jezik can mean:

• a language
• the language

The exact meaning depends on context.

In this sentence, if the meaning has already been provided, the learner should know whether it means a language in general or some specific language understood from context.

Because na here means on or at, referring to location, and that requires the locative case.

The noun računar changes like this:

• nominative: računar
• locative: računaru

So:

• na računaru = on the computer

This is a very common pattern in Serbian:

• na stolu = on the table
• na poslu = at work
• na internetu = on the internet

Yes, literally it is on the computer.

In natural English, depending on context, you might also say:

• on the computer
• using a computer
• sometimes at the computer

But the Serbian phrase itself is the normal way to express doing something on a computer.

Yes. Both are used.

• računar is the native/standard Serbian word for computer
• kompjuter is also very common in everyday speech

So both of these are natural:

• Učim jezik na računaru.
• Učim jezik na kompjuteru.

Usage can depend on region, style, or personal preference.

Serbian word order is more flexible than English word order.

This sentence can be rearranged in several ways without changing the core meaning:

• Ja ponekad učim jezik na računaru.
• Ponekad učim jezik na računaru.
• Jezik ponekad učim na računaru.
• Na računaru ponekad učim jezik.

However, different word orders can sound more natural in different situations, and they can shift emphasis.

For a neutral statement, the most natural versions are usually:

• Ponekad učim jezik na računaru.
• Ja ponekad učim jezik na računaru.

Usually it means I am learning a language or I study a language.

In Serbian, učiti is broad. It can mean:

• to learn
• to study
• to be learning

So učim jezik most naturally means that the speaker is learning some language.

If you wanted to say I study linguistics/language as a field, Serbian would usually use a more specific expression, not just učim jezik.

A rough guide:

• učim ≈ OO-chim
• računaru ≈ rah-choo-NA-roo

A few helpful sound notes:

• č sounds like ch in church
• ć is a softer sound than č
• š sounds like sh
• ž sounds like the s in measure
• j sounds like English y

So:

• ja sounds like ya
• jezik sounds roughly like YE-zik
• računaru has č, the stronger ch sound

Because jezik simply means language.

This sentence is generic. It does not tell you which language is being learned. If you want to name the language, you would normally say it directly:

• Učim srpski. = I’m learning Serbian.
• Učim engleski. = I’m learning English.
• Učim nemački. = I’m learning German.

So učim jezik is more general, while učim srpski is specific.

Normally, for this meaning, na računaru is the natural choice.

Serbian commonly uses na for activities done on devices, platforms, or surfaces:

• na telefonu = on the phone
• na internetu = on the internet
• na televiziji = on TV

Using a different preposition here would usually sound unnatural or change the meaning. So for on the computer, na računaru is the standard phrase.