Proszę pani, chodzi mi o znaczenie tego wyrażenia, a nie o jego tłumaczenie.

It is a polite way to address a woman, something like ma’am, excuse me, ma’am, or, in a school setting, miss/teacher depending on context.

In this sentence, it is not really part of the main grammar of chodzi mi o.... It is just a polite opener used to get the listener’s attention.

Polish uses pan and pani as polite forms of address. In expressions like Proszę pani, the normal form is simply pani.

So even if a learner expects a special vocative ending, Polish does not use one here. Proszę pani is the standard expression.

Chodzi mi o is a very common Polish pattern meaning:

• I mean
• I’m referring to
• what I’m asking about is
• I’m concerned with

It should be learned as a whole expression: komuś chodzi o coś.

Also, even though chodzić often means to go or to walk, in chodzić o it has a different idiomatic meaning: to be about / to concern.

Because the pattern is komuś chodzi o coś, so it needs the dative form of the pronoun.

• mi = short, unstressed dative form of I / me
• mnie = longer form, often used for emphasis
• ja would be wrong here

So:

• Chodzi mi o znaczenie = neutral, natural
• Mnie chodzi o znaczenie = possible, but more emphatic

In chodzić o coś, the preposition o takes the accusative.

That is why we get:

• o znaczenie
• o tłumaczenie

These nouns are neuter and inanimate, so their accusative form looks the same as the nominative form.

This is worth noticing because o does not always take the same case in Polish. For example:

• chodzić o coś → accusative
• rozmawiać o czymś → locative

Because Polish expresses the meaning of this expression as:

• znaczenie = meaning
• tego wyrażenia = of this expression

After znaczenie, Polish uses the genitive to show of something:

• znaczenie czego? = meaning of what?
• znaczenie tego wyrażenia

So wyrażenie changes to wyrażenia, and ten changes to tego to match it.

Because wyrażenie is a neuter singular noun, and here it is in the genitive singular.

So the forms are:

• nominative: to wyrażenie
• genitive: tego wyrażenia

A learner often notices tego because it can be used for both masculine and neuter nouns in the genitive singular.

Because jego refers back to wyrażenie and avoids repetition.

So:

• o jego tłumaczenie = about its translation

You could also say:

• a nie o tłumaczenie tego wyrażenia

That is also correct, but a bit more repetitive.

Here it means its.

Polish jego can mean:

• his
• its

The context tells you which one is meant. In this sentence, it clearly refers to wyrażenie (expression), not to a male person.

A nie is the normal way to contrast two things in Polish:

• X, a nie Y = X, not Y / X rather than Y

So here:

• o znaczenie..., a nie o tłumaczenie
  = about the meaning, not about the translation

Ale nie usually sounds more like a stronger contradiction of a statement, so a nie is the more natural choice here.

There are two commas for two different reasons:

• Proszę pani,
  The first comma separates the form of address from the rest of the sentence.

• ..., a nie o jego tłumaczenie.
  The second comma comes before a nie, which introduces a contrast.

So the commas help show the structure clearly.

Not completely. Polish word order is fairly flexible, but this version is the most neutral and natural.

• Chodzi mi o znaczenie tego wyrażenia... = normal
• Mnie chodzi o znaczenie tego wyrażenia... = emphasizes me
• O znaczenie tego wyrażenia mi chodzi... = possible, but marked and less neutral

So the original sentence is a good standard version to learn.

Yes. Some natural alternatives are:

• Nie chodzi mi o tłumaczenie tego wyrażenia, tylko o jego znaczenie.
• Mam na myśli znaczenie tego wyrażenia, a nie jego tłumaczenie.

These are slightly different in style, but they express the same basic idea.