Jeśli ktoś ma duży dług, powinien szybko porozmawiać z bankiem.

Jeśli means if.

In this sentence, Jeśli ktoś ma duży dług... = If someone has a large debt...

Yes, jeśli and jeżeli usually mean the same thing.
The difference is mostly style:

• jeśli is very common and natural in everyday speech
• jeżeli can sound a little more formal or careful

So you could also say:

• Jeżeli ktoś ma duży dług, powinien szybko porozmawiać z bankiem.

Both are correct.

Because Polish, like English, normally uses a comma after an if-clause when it comes first.

So:

• Jeśli ktoś ma duży dług, powinien szybko porozmawiać z bankiem.

The first part is the condition: If someone has a large debt
The second part is the main statement: they should quickly talk to the bank

This comma is standard and expected.

Ktoś means someone or somebody.

It is an indefinite pronoun, used when you are talking about a person in a general, non-specific way.

So:

• Jeśli ktoś ma duży dług... = If someone has a large debt...

It does not refer to a particular person. It means any person in that situation.

Yes. Literally, ma duży dług means has a big/large debt.

Breakdown:

• ma = has
• duży = big / large
• dług = debt

Polish often uses mieć dług / mieć długi where English might say:

• to have a debt
• to be in debt
• to have large debts

So the Polish phrasing is very normal.

Because dług is the direct object of ma (has), so it is in the accusative case.

However, for a masculine inanimate noun like dług, the accusative singular looks the same as the nominative singular.

So:

• nominative: duży dług
• accusative: duży dług

That is why the form does not visibly change here.

If this were a masculine animate noun, you would see a clearer difference. But with dług, nominative and accusative are identical in the singular.

Yes, powinien here means should.

It expresses advice, recommendation, or what is considered the right thing to do.

So:

• powinien szybko porozmawiać z bankiem = should quickly talk to the bank

It is softer than must.

Compare:

• powinien = should
• musi = must / has to

So this sentence gives advice, not a strict command.

Because powinien is the masculine singular form, and Polish often uses this form in general statements when the person is unspecified.

Here the subject is ktoś (someone), which is grammatically singular. In many contexts, Polish uses the masculine singular as the default general form.

You may also hear or see more gender-specific versions in other contexts:

• powinien = he should
• powinna = she should
• powinni = they should (mixed group or all-male group)
• powinny = they should (all-female group or some non-masculine plural groups)

In this sentence, powinien is the normal general form after ktoś.

This is about aspect, which is very important in Polish verbs.

• rozmawiać = imperfective, to be talking / to talk in a general or ongoing sense
• porozmawiać = perfective, to have a talk / to talk for a bit / to talk and complete that action

In this sentence, the speaker means have a conversation with the bank as a practical step. That is why porozmawiać fits well: it suggests a concrete, completed action.

So:

• powinien porozmawiać z bankiem = he/she should talk to the bank
  meaning: they should go and have that conversation

If you said powinien rozmawiać z bankiem, it would sound more like:

• he/she should be talking with the bank
• he/she should maintain communication with the bank

That is a bit different.

Because the preposition z meaning with requires the instrumental case.

The noun bank in the instrumental singular becomes:

• bank → bankiem

So:

• z bankiem = with the bank

This is a very common pattern in Polish:

• z kolegą = with a friend
• z mamą = with mum
• z lekarzem = with a doctor
• z bankiem = with the bank

Be careful: z can also mean from, but then it does not take the instrumental. Here it clearly means with, so bankiem is correct.

Szybko means quickly or soon.

In this sentence, it means the person should not delay:

• powinien szybko porozmawiać z bankiem = should talk to the bank quickly / should talk to the bank soon

Its position is flexible, but the given placement sounds natural:

• powinien szybko porozmawiać z bankiem

You could also hear:

• powinien porozmawiać szybko z bankiem
  but this sounds less natural

A very natural alternative is:

• powinien jak najszybciej porozmawiać z bankiem = should talk to the bank as soon as possible

Yes, Polish word order is more flexible than English word order, but that does not mean every order sounds equally natural.

The neutral version is:

• Jeśli ktoś ma duży dług, powinien szybko porozmawiać z bankiem.

You could also say:

• Jeśli ktoś ma duży dług, z bankiem powinien szybko porozmawiać.

That is grammatically possible, but it puts more emphasis on z bankiem and sounds less neutral.

In most learning situations, it is best to keep the standard order unless you have a reason to emphasize something.

Yes, but it would slightly change the meaning.

• duży dług = a large debt (one large debt, or debt treated as one amount)
• duże długi = large debts / a lot of debt obligations

So:

• Jeśli ktoś ma duży dług... focuses on one serious debt, or debt as a single large burden.
• Jeśli ktoś ma duże długi... suggests multiple debts or more of a general debt problem.

Both are possible, depending on what you want to say.

It is fairly neutral.

Nothing in it is especially casual or especially formal. It would work in:

• advice articles
• financial guidance
• normal conversation
• educational materials

If you wanted to sound more formal, you might change a few words, but this sentence is already very natural and standard Polish.