Chcę zakwestionować decyzję.

In Polish, subject pronouns are often omitted because the verb already shows who is doing the action.

• Chcę = I want
• so ja (I) is not necessary

You could say:

• Ja chcę zakwestionować decyzję.

But that usually adds emphasis, as in:

• I want to challenge the decision.

So the version without ja is the most natural neutral form.

Chcę is the 1st person singular present tense form of chcieć (to want).

So:

• chcieć = to want
• chcę = I want

Other related forms are:

• chcesz = you want
• chce = he/she/it wants
• chcemy = we want
• chcecie = you all want
• chcą = they want

In this sentence, chcę is followed by an infinitive:

• Chcę zakwestionować... = I want to challenge...

After chcę (I want), Polish commonly uses an infinitive, just like English uses to + verb.

So the pattern is:

• chcę + infinitive

Examples:

• Chcę iść. = I want to go.
• Chcę przeczytać książkę. = I want to read a book.
• Chcę zakwestionować decyzję. = I want to challenge the decision.

So zakwestionować is simply the verb to challenge / to question / to dispute in its dictionary form.

This is an important aspect question.

• kwestionować is imperfective
• zakwestionować is perfective

Very roughly:

• kwestionować = to be questioning / to question in a general or ongoing sense
• zakwestionować = to challenge/question something as a completed act

In this sentence, zakwestionować suggests making a definite challenge to the decision.

Compare:

• Chcę kwestionować tę decyzję.
  = I want to question/challenge this decision (more process-like, less bounded)

• Chcę zakwestionować tę decyzję.
  = I want to challenge this decision (a single, concrete act)

With chcę, both aspects are possible, but they give slightly different nuances.

Because decyzję is in the accusative case, which is used here for the direct object of the verb.

• decyzja = decision (nominative, dictionary form)
• decyzję = decision (accusative singular)

In this sentence, the thing being challenged is the decision, so Polish uses the accusative:

• Chcę zakwestionować decyzję.

This is very common with feminine nouns ending in -a:

• książka → książkę
• sprawa → sprawę
• decyzja → decyzję

Because decyzja is a feminine singular noun ending in -a, and for many feminine nouns, the accusative singular changes:

• -a → -ę

So:

• decyzja → decyzję

This is one of the most important case patterns in Polish.

More examples:

• mam kawę from kawa
• widzę kobietę from kobieta
• rozumiem sprawę from sprawa

So decyzję follows a very regular pattern.

No, Polish word order is more flexible than English, because case endings help show grammatical roles.

The most neutral word order here is:

• Chcę zakwestionować decyzję.

But other orders are possible for emphasis, for example:

• Decyzję chcę zakwestionować.
  Emphasizes the decision
• Zakwestionować chcę decyzję.
  More marked; emphasizes the action itself

Even though these are possible, the original sentence is the most natural neutral version.

A rough pronunciation guide for an English speaker is:

• Chcę ≈ h-tsen / h-tseh(n)
• zakwestionować ≈ zah-kvyes-tyo-NO-vach
• decyzję ≈ deh-TSIZ-yeh

A few useful notes:

• ch sounds like the ch in Scottish loch or German Bach
• cz is not used here, but c in decyzję sounds like ts
• w in Polish sounds like English v
• stress in Polish usually falls on the second-to-last syllable

So the stress is:

• zakwestioNOwać
• deCYZję

Yes, it is fairly formal and is often used in official, legal, administrative, academic, or serious contexts.

So Chcę zakwestionować decyzję sounds like:

• I want to challenge the decision
• I want to dispute the decision

This is more formal than everyday conversational verbs such as:

• podważyć = to undermine / challenge
• sprzeciwić się = to object
• nie zgodzić się z decyzją = to disagree with the decision

So this sentence sounds quite appropriate in contexts like:

• bureaucracy
• appeals
• complaints
• legal disputes
• workplace procedures

Yes, you can, but the nuance changes slightly.

• zakwestionować decyzję = to challenge/question the validity or correctness of the decision
• podważyć decyzję = to undermine or cast doubt on the decision

Both can work, but zakwestionować often sounds especially suitable when you are formally contesting something.

If you are talking about an appeal, complaint, or official objection, zakwestionować decyzję is a very strong and natural choice.

It only states wanting or intending to do it.

• Chcę zakwestionować decyzję. = I want to challenge the decision.

It does not mean the challenge has already happened.

If you want to say that you actually did it, you would need a different sentence, for example:

• Zakwestionowałem decyzję. = I challenged the decision.
  (said by a man)
• Zakwestionowałam decyzję. = I challenged the decision.
  (said by a woman)

So the original sentence expresses intention, not completion.

A literal breakdown is:

• Chcę = I want
• zakwestionować = to challenge / to question / to dispute
• decyzję = the decision / a decision

So the structure is:

• I want + to challenge + decision

Since Polish often does not use articles like a and the, decyzję can mean:

• a decision
• the decision

The exact meaning depends on context. In many situations, English will naturally translate it as the decision.