Ona urodziła się w lipcu, a ja urodziłem się w listopadzie.

Because Polish past tense agrees with gender as well as person and number.

• ona urodziła się = she was born
• ja urodziłem się = I was born said by a man
• If the speaker were a woman, it would be ja urodziłam się

So in this sentence, ona refers to a female person, and ja is a male speaker.

In Polish, urodzić się is the normal way to say to be born.

So:

• urodzić by itself usually means to give birth to
• urodzić się means to be born

Even though się often looks like oneself, here you should learn urodzić się as a fixed expression meaning be born.

Because after the preposition w meaning in, the names of months take the locative case.

So:

• lipiec → w lipcu
• listopad → w listopadzie

This is just the normal pattern for months when saying in July, in November, etc.

A often links two clauses with a slight sense of contrast or comparison.

So:

• Ona urodziła się w lipcu, a ja urodziłem się w listopadzie.

means something like:

• She was born in July, and I was born in November
• or She was born in July, whereas I was born in November

If you used i, it would sound more like simple addition. A is very natural here because the sentence compares her month with my month.

Because Polish does not need a separate auxiliary verb here.

In English, you say:

• she was born
• I was born

In Polish, the past form itself already carries that meaning:

• urodziła się
• urodziłem się

So the idea of was born is expressed by the verb form, not by a separate word like was.

Yes, very often.

Polish usually drops subject pronouns when they are clear from the verb form or the context. So you could say:

• Urodziła się w lipcu, a ja urodziłem się w listopadzie.

That is completely natural.

Including ona adds emphasis or contrast, especially because the sentence compares her and me.

Sometimes yes, but here it is usually kept because it helps the contrast.

You could say:

• Ona urodziła się w lipcu, a urodziłem się w listopadzie.

and it could be understood, but it sounds less balanced. In a comparison like this, ja is very natural and usually preferred.

So in this sentence:

• ona = optional, often used for emphasis
• ja = also not strictly necessary, but very natural here

Because urodziłem się is first person singular: I was born.

Compare:

• urodził się = he was born
• urodziłem się = I was born said by a man
• urodziłam się = I was born said by a woman

The ending -em marks I in the masculine form.

Yes. Urodzić się is perfective, and that matters because being born is treated as a completed single event.

That is why Polish normally says:

• urodził się / urodziła się / urodziłem się

for was born.

There is also rodzić się, which is imperfective, but it is not the normal choice for a simple statement about someone’s date of birth. For this sentence, urodzić się is exactly right.

Yes. Polish word order is more flexible than English.

All of these can work:

• Ona urodziła się w lipcu
• Ona się urodziła w lipcu

The first version is probably the most neutral for many learners.
A useful rule is that się usually does not go at the very beginning of a clause.

So:

• Się urodziła... is not a normal way to begin the sentence
• but Ona się urodziła... is fine

It depends on the speaker’s gender.

• If you are male: urodziłem się
• If you are female: urodziłam się

This is one of the important things English speakers need to get used to in Polish: in the past tense, you often reveal your gender in the verb form.

It simply means in November. Polish does not use articles like a or the, so the exact meaning comes from context.

In this sentence, it naturally means in the month of November when I was born. There is no need for an article in Polish.