Én a könyvtárban olvasok, a barátom pedig a parkban sétál.

That is correct: Hungarian usually does not need subject pronouns, because the verb ending already shows who is doing the action.

• olvasok already means I read / I am reading
• sétál already means he/she walks / is walking

So Én a könyvtárban olvasok could simply be A könyvtárban olvasok.

Here, én is included for contrast or emphasis. It gives the sense of:

• I am reading in the library, while my friend is walking in the park.

So én is not required for grammar, but it helps create a contrast with a barátom.

Pedig is a very common Hungarian connecting word that often means:

• while
• whereas
• as for
• sometimes a contrastive and

In this sentence, it connects two parallel ideas and highlights a contrast:

• I am reading in the library
• my friend, meanwhile / whereas, is walking in the park

So pedig is stronger and more contrastive than a simple and.

Because pedig is linking two separate clauses, and each clause has its own verb:

• Én a könyvtárban olvasok
• a barátom pedig a parkban sétál

In Hungarian, when two clauses are connected in this way, a comma is normally used. So the comma here is standard punctuation.

The ending -ban / -ben means in.

So:

• könyvtárban = in the library
• parkban = in the park

This is called the inessive ending in Hungarian.

The choice between -ban and -ben follows vowel harmony:

• -ban is used after back vowels
• -ben is used after front vowels

Here both könyvtár and park take -ban.

A is the Hungarian definite article, meaning the.

So:

• a könyvtárban = in the library
• a parkban = in the park

Hungarian uses definite articles in many cases where English uses the, so this is very natural here.

In Hungarian, possession is usually shown with an ending attached directly to the noun.

So:

• barát = friend
• barátom = my friend

The ending -om here means my.

This is very typical in Hungarian:

• könyvem = my book
• házam = my house
• barátom = my friend

So Hungarian often uses a possessive ending instead of a separate word like my.

Because the definite article and the possessive ending do different jobs.

• barátom tells you whose friend: my friend
• a marks the noun as definite in the sentence

So a barátom is completely normal Hungarian and means my friend in a full sentence.

This often feels unusual to English speakers, because English does not say the my friend. But Hungarian structure is different.

Because Hungarian verbs change form depending on the subject.

Here:

• olvasok = I read / I am reading
• sétál = he/she walks / is walking

So:

• -ok shows first person singular: I
• sétál is third person singular: he/she

Hungarian does this regularly, which is why subject pronouns can often be left out.

It can mean either one, depending on context.

Hungarian present tense often covers both:

• I read
• I am reading

So:

• olvasok can mean I read or I am reading
• sétál can mean he/she walks or he/she is walking

English makes a stronger distinction here than Hungarian does.

Yes. Hungarian word order is quite flexible, but changes in order often change emphasis rather than basic meaning.

For example:

• Én a könyvtárban olvasok puts emphasis on én, especially in contrast with a barátom
• A könyvtárban olvasok sounds more neutral
• Olvasok a könyvtárban is also possible, with a different information structure

So the word order in your sentence is not random. It helps create the contrast:

• I am reading in the library,
• my friend, on the other hand, is walking in the park.

Yes, very much. In Hungarian, accent marks are part of the spelling and pronunciation.

For example:

• é
• á

are not optional marks; they represent different vowels from the unaccented versions.

So:

• Én must be written with É
• sétál must be written with é and á

For learners, it is best to treat accented vowels as full, separate vowel letters, not just decorative marks.