Policjant pomaga ofierze.

Because ofiara changes form here. The verb pomagać (to help) takes the dative case, so ofiara becomes ofierze.

So:

• ofiara = victim in the dictionary form, nominative
• ofierze = to the victim, dative

In this sentence, Polish is really saying something like The policeman helps to the victim, and that is why the noun changes.

Ofierze is in the dative singular.

A very useful thing to remember is:

• pomagać
  • dative

So if someone helps someone, the person receiving help is usually in the dative:

• Pomagam mamie. = I help my mother.
• Pomaga dziecku. = He/She helps the child.
• Policjant pomaga ofierze. = The policeman helps the victim.

Because policjant is the subject of the sentence, so it stays in the nominative case.

Here:

• policjant = the one doing the action
• ofierze = the one receiving the help

Polish often marks roles in a sentence by case endings, not just by word order.

You know because of the cases.

• policjant is nominative, so it is the subject
• ofierze is dative, so it is the person being helped

Even if the word order changes, the case endings still show the roles.

For example:

• Policjant pomaga ofierze.
• Ofierze pomaga policjant.

Both mean The policeman helps the victim.

Yes. Polish word order is more flexible than English.

The neutral order here is:

• Policjant pomaga ofierze.

But you could also say:

• Ofierze pomaga policjant.

This might put more focus on the victim.

Because of the case ending -e in ofierze, Polish speakers still understand who receives the help.

Because pomagać is the infinitive form, meaning to help.

In the sentence, you need the conjugated form:

• pomagać = to help
• pomaga = he/she/it helps

So:

• Policjant pomaga = The policeman helps

Here pomaga is 3rd person singular present tense.

It can mean either, depending on context.

Polish present tense often covers both:

• helps
• is helping

So Policjant pomaga ofierze could mean:

• The policeman helps the victim
• The policeman is helping the victim

Context tells you which is more natural.

A learner may find it helpful to see the pattern:

• nominative: ofiara
• genitive: ofiary
• dative: ofierze
• accusative: ofiarę
• instrumental: ofiarą
• locative: ofierze

So in your sentence, ofierze is the expected dative form.

No. Polish does not use articles like English a/an and the.

So Policjant pomaga ofierze could mean:

• A policeman helps a victim
• The policeman helps the victim

Which one is meant depends on context.

A rough English-style guide is:

• Policjant ≈ po-LEE-tsyant
• pomaga ≈ po-MA-ga
• ofierze ≈ o-FYE-zhe

A few useful pronunciation notes:

• cj in policjant sounds roughly like tsy
• g in pomaga is always a hard g, like in go
• rz in ofierze sounds like the zh sound in measure

Then you would normally say:

• Policjantka pomaga ofierze.

So:

• policjant = male police officer / policeman
• policjantka = female police officer / policewoman

The rest of the sentence stays the same because ofierze is still dative after pomaga.