W tym ćwiczeniu chodzi o pisownię, a nie o szybkie czytanie.

Yes, it does come from chodzić, but in chodzi o it is part of a fixed expression and is not understood literally as walks about.

chodzi o + accusative means:

• it is about
• it concerns
• the point is
• what matters is

So:

• W tym ćwiczeniu chodzi o pisownię
  = In this exercise, it’s about spelling
  = more naturally, This exercise is about spelling

This is a very common Polish structure.

Because the preposition w here means in and refers to location or context, so it requires the locative case.

Base form:

• to ćwiczenie = this exercise / that exercise in nominative

After w:

• w tym ćwiczeniu = in this exercise

Both words change to match the locative:

• ten / to → tym
• ćwiczenie → ćwiczeniu

So the pattern is:

• to ćwiczenie
• w tym ćwiczeniu

Because chodzi o takes the accusative case, and pisownia changes in the accusative singular:

• nominative: pisownia
• accusative: pisownię

So:

• chodzi o pisownię = it is about spelling

This is very common with o after certain verbs and expressions. Here, you should think of chodzi o + accusative as one unit.

Because in Polish, when you contrast two phrases introduced by the same preposition, you normally repeat the preposition.

So the structure is:

• o X, a nie o Y

Here:

• o pisownię, a nie o szybkie czytanie

That repeated o sounds natural and clear in Polish. English often omits repeated prepositions more easily, but Polish usually keeps them.

In this sentence, a nie is the most natural way to make a contrast between two alternatives:

• about spelling, not about fast reading

Polish a often introduces contrast, especially between two parallel ideas.

So:

• o pisownię, a nie o szybkie czytanie

means something like:

• spelling, not fast reading

ale nie is possible in some contexts, but it usually sounds more corrective or emphatic. Here, a nie is the normal choice.

Because czytanie here is a noun, not a finite verb.

• czytanie = reading
• szybkie czytanie = fast reading

Since it is a noun phrase, it is modified by an adjective:

• szybki / szybka / szybkie = fast

So:

• szybkie czytanie = fast reading

By contrast:

• szybko czytać = to read quickly

Here szybko is an adverb, because it modifies the verb czytać.

So the difference is:

• szybkie czytanie = noun phrase
• szybko czytać = verb phrase

In this sentence, czytanie is a noun, specifically a verbal noun formed from the verb czytać (to read).

It works much like an English -ing noun in some contexts:

• czytać = to read
• czytanie = reading

It behaves grammatically like a normal neuter noun. That is why it can be modified by an adjective:

• szybkie czytanie = fast reading

And after o, it appears in the accusative. For a neuter inanimate noun like czytanie, nominative and accusative have the same form, so you still see czytanie.

tym is the form of the demonstrative ten / ta / to that matches the case, gender, and number of ćwiczeniu.

The basic idea is:

• to ćwiczenie = this exercise

But after w, you need the locative:

• w tym ćwiczeniu = in this exercise

So tym is simply this in the correct case form for this sentence.

Because a is a coordinating conjunction, and in standard Polish spelling it is normally preceded by a comma when it links two contrasting parts of a sentence.

So:

• ..., a nie ...

is the correct written form.

Since the sentence itself talks about pisownia (spelling/orthography), the punctuation here is especially worth noticing.

Yes, Polish word order is fairly flexible, although different orders can sound more neutral, more emphatic, or more contrastive.

The original sentence:

• W tym ćwiczeniu chodzi o pisownię, a nie o szybkie czytanie.

is natural and neutral.

You could also say:

• W tym ćwiczeniu nie chodzi o szybkie czytanie, a o pisownię.

That version puts stronger emphasis on correcting a possible misunderstanding: not fast reading, but spelling.

So the original is a very good standard version, but other orders are possible depending on emphasis.

Usually yes, in a sentence like this.

pisownia refers to the way words are written correctly, so in this context it means:

• spelling
• sometimes more broadly, orthography

So:

• chodzi o pisownię
  means the task is focused on correct written form, not on speed of reading.

That is why it contrasts naturally with szybkie czytanie.