Nazwisko mojej koleżanki ma trzynaście liter, więc zawsze piszę je powoli.

Because Polish is using the genitive case to show possession.

• koleżanka = the basic dictionary form, nominative
• koleżanki = genitive singular

So:

• nazwisko koleżanki = the colleague’s / female friend’s surname
• literally: surname of my female friend

This is a very common Polish pattern:

• dom mojej siostry = my sister’s house
• imię mojego brata = my brother’s name

Because mojej has to match koleżanki in gender, number, and case.

The noun koleżanka is:

• feminine
• singular
• genitive here

So the possessive word moja changes to mojej.

Compare:

• moja koleżanka = my female friend/colleague
• nazwisko mojej koleżanki = my female friend’s surname

Nazwisko is neuter.

Even though it refers to something connected with a person, its grammatical gender is based on the noun itself, not on the person. Many Polish nouns ending in -o are neuter.

That matters later in the sentence because the pronoun referring to it is je.

Ma is the 3rd person singular present form of mieć = to have.

The subject is nazwisko mojej koleżanki, so Polish uses ma:

• ono ma = it has

In the present tense, Polish uses the same form ma for:

• on ma = he has
• ona ma = she has
• ono ma = it has

Because after numbers 5 and higher, Polish usually puts the counted noun in the genitive plural.

• litera = letter
• liter = of letters / letters after 5+

So:

• dwie litery = two letters
• trzy litery = three letters
• cztery litery = four letters
• pięć liter = five letters
• trzynaście liter = thirteen letters

This is one of the most important number patterns in Polish.

Here je means it.

It refers back to nazwisko:

• piszę je = I write it

Why je? Because nazwisko is neuter singular, and here it is the direct object of piszę.

A useful note: je can also mean them in other contexts, so you understand it from grammar and context.

Because piszę comes from the imperfective verb pisać, which is the normal choice for repeated, habitual, or ongoing actions.

Here we have zawsze = always, so a habitual meaning is needed:

• zawsze piszę je powoli = I always write it slowly

If you used napiszę, that would be the perfective future:

• napiszę = I will write / I will finish writing

So piszę is the natural choice in this sentence.

Powoli means slowly.

It is an adverb, so it describes how the action is done:

• piszę powoli = I write slowly

You need an adverb here because it modifies the verb piszę.

Compare:

• powolny = slow (adjective, describing a noun)
• powoli = slowly (adverb, describing a verb)

Because więc means so / therefore, and here it connects two clauses:

• Nazwisko mojej koleżanki ma trzynaście liter
• więc zawsze piszę je powoli

In Polish, when więc joins clauses like this, it is normally preceded by a comma.

Koleżanka usually means a female friend, colleague, classmate, or acquaintance, depending on context.

It is broader and often less emotionally strong than przyjaciółka, which usually means a close female friend.

So moja koleżanka could be:

• my female friend
• my female colleague
• my classmate

The exact English translation depends on the situation.

Yes — all of those can work in English.

In Polish:

• imię = first name / given name
• nazwisko = surname / last name / family name

So nazwisko mojej koleżanki is her surname or last name.

Not completely. Polish word order is more flexible than English word order.

This version sounds natural and neutral:

• Nazwisko mojej koleżanki ma trzynaście liter, więc zawsze piszę je powoli.

Why this order works well:

• Nazwisko mojej koleżanki is introduced first as the topic
• więc introduces the result
• je stays close to the verb phrase

You can change word order for emphasis, but some versions sound more natural than others. So the sentence is not the only possible order, but it is a very good standard one.