U radnoj biografiji sam opisala iskustvo i veštine.

Because the preposition u here means in and expresses location, so it requires the locative case.

The basic form is:

• radna biografija = work biography / CV / résumé

In the locative singular, it becomes:

• radnoj biografiji

Both words change because the adjective must agree with the noun:

• radna → radnoj
• biografija → biografiji

So u radnoj biografiji means in the work biography / in the CV.

Radna biografija is a formal expression for a person’s employment history, professional biography, or sometimes simply a CV/résumé, depending on context.

A learner should know that Serbian can also use:

• CV
• biografija
• radna biografija

So this phrase sounds a bit more formal or administrative than everyday English resume.

Sam opisala is the past tense.

Serbian past tense is usually formed with:

• the present tense of biti (to be)
• plus the past participle

Here:

• sam = I am / have as an auxiliary
• opisala = past participle of opisati (to describe)

Together, sam opisala means:

• I described
• or sometimes I have described, depending on context

In standard grammatical terms, this is the Serbian perfect.

Because the speaker is female.

In Serbian past tense, the participle agrees with the gender of the subject:

• opisao = a man said it
• opisala = a woman said it

So:

• Ja sam opisao... = I described... (male speaker)
• Ja sam opisala... = I described... (female speaker)

This is a very common feature of Serbian and other Slavic languages.

Serbian often leaves out subject pronouns when they are already clear from the verb form and context.

So instead of saying:

• Ja sam opisala iskustvo i veštine.

it is very natural to say:

• Sam opisala iskustvo i veštine.

However, in this particular sentence, the I is understood from sam and opisala.

If you want extra emphasis, contrast, or clarity, you can include ja:

• Ja sam opisala iskustvo i veštine.

That would sound like I described the experience and skills with a bit more emphasis on I.

Because sam is a clitic, and Serbian clitics usually go in second position in the sentence or clause.

That is why the sentence begins:

• U radnoj biografiji sam...

The first unit is U radnoj biografiji, and then the clitic sam comes right after it.

This is normal Serbian word order.

Compare:

• U radnoj biografiji sam opisala...
• Ja sam opisala...
• Iskustvo sam opisala...

In each case, sam tends to appear after the first element or phrase.

They are in the accusative case because they are the direct objects of opisala (described).

The speaker described what?

• iskustvo = experience
• veštine = skills

So both are objects of the verb.

However, they look the same as the nominative here:

• iskustvo is a neuter singular noun, and nominative = accusative
• veštine is a feminine plural noun, and nominative plural = accusative plural

So even though the case is accusative, the forms do not visibly change.

Because that is how these words are commonly used.

• iskustvo often works like English experience as a mass or abstract noun
• veštine is usually plural, like skills

So iskustvo i veštine is a very natural combination meaning something like:

• experience and skills

You could sometimes see plural iskustva if the speaker means specific experiences, but iskustvo is the most natural general choice here.

The infinitive is opisati.

This verb is perfective, which means it presents the action as completed: to describe, to write up, to give a description of as a finished act.

Its imperfective partner is usually:

• opisivati = to be describing / to describe repeatedly or in an ongoing way

So in this sentence, opisala suggests a completed action: the speaker finished describing her experience and skills in the CV.

Yes, Serbian word order is flexible, but not all versions sound equally natural in all contexts.

The given sentence:

• U radnoj biografiji sam opisala iskustvo i veštine.

is neutral and natural.

Possible alternatives include:

• Iskustvo i veštine sam opisala u radnoj biografiji.
• Opisala sam iskustvo i veštine u radnoj biografiji.

These are also grammatical, but the focus changes slightly:

• starting with U radnoj biografiji emphasizes where
• starting with Iskustvo i veštine emphasizes what
• starting with Opisala sam emphasizes the action itself a bit more

So the original sentence is just one natural way to arrange the information.

Both are correct, but they belong to different pronunciation standards.

• veštine = Ekavian
• vještine = Ijekavian

Serbian is commonly written in both varieties depending on region and standard usage. So if you see:

• iskustvo i veštine
• iskustvo i vještine

the meaning is the same.

No. Here u is the correct choice.

• u = in, inside a document or text
• na is used for some surfaces, events, institutions, websites, and other contexts, but not here

Because the meaning is in the CV / in the professional biography, Serbian uses:

• u radnoj biografiji

So na radnoj biografiji would sound wrong or at least very unnatural in this context.

Yes. Serbian past tense in sentences like this can correspond to either English simple past or present perfect, depending on context.

So sam opisala could be translated as:

• I described
• I have described

English chooses between those two more strictly than Serbian does. Serbian often uses the same past form where English might choose one or the other based on context.