Dzieci uczą się alfabetu, bo chcą lepiej czytać po polsku.

Dzieci means children. It is the plural form of dziecko (child).

So:

• dziecko = child
• dzieci = children

Since the verb is plural too (uczą się, chcą), the subject has to be plural.

Uczą się means are learning / learn.

The basic verb is uczyć się = to learn.

That się is part of the verb. In Polish, many verbs include się, and you often just need to learn them that way as a whole expression.

A very useful contrast is:

• uczyć kogoś = to teach someone
• uczyć się = to learn

So:

• Dzieci uczą się alfabetu = The children are learning the alphabet

Because uczyć się commonly takes the genitive case.

The noun alfabet becomes alfabetu in the genitive singular:

• alfabet = alphabet
• alfabetu = of the alphabet

So after uczyć się, Polish often uses:

• uczyć się czegoś = to learn something

Here:

• uczyć się alfabetu = to learn the alphabet

For an English speaker, this can feel strange because English does not change alphabet in this way.

Yes, it is present tense.

In Polish, the present tense can often cover both:

• learn
• are learning

So Dzieci uczą się alfabetu could mean:

• Children learn the alphabet
• The children are learning the alphabet

The exact meaning depends on context. In this sentence, the natural English translation is usually are learning.

Because bo introduces a clause meaning because, and in Polish it is standard to put a comma before it.

So:

• Dzieci uczą się alfabetu, bo chcą lepiej czytać po polsku.

This is normal Polish punctuation.

Yes, bo means because.

It is very common and natural in everyday Polish.

You may also see ponieważ, which also means because, but bo is often more conversational and common in speech.

So here:

• bo chcą... = because they want...

After chcą (they want), Polish normally uses the infinitive of the next verb.

So:

• chcą czytać = they want to read

Notice that Polish does not need a separate word for to here. English says want to read, but Polish simply uses:

• chcą czytać

The verb chcą is the 3rd person plural form of chcieć = to want.

Lepiej means better.

It is the comparative form of dobrze (well):

• dobrze = well
• lepiej = better

So:

• czytać dobrze = to read well
• czytać lepiej = to read better

In this sentence, lepiej shows improvement: they want to read better than before.

Po polsku means in Polish.

It is a very common Polish pattern for languages:

• po angielsku = in English
• po polsku = in Polish
• po niemiecku = in German

So czytać po polsku means to read in Polish.

This phrase is adverbial: it describes how / in what language the reading happens.

Because after po in this language expression, Polish uses a special adverb-like form ending in -sku.

So you say:

• po polsku
• po angielsku
• po francusku

Not:

• po polski ❌

This is something you mostly learn as a fixed pattern.

It most naturally means to read in Polish.

That is, the children want to become better at reading texts written in the Polish language.

English sometimes says read Polish, but Polish often expresses this with:

• czytać po polsku = read in Polish

Both verbs are in the 3rd person plural because dzieci is plural.

You can see that in:

• uczą się = they learn / are learning
• chcą = they want

So the sentence structure is:

• Dzieci = subject
• uczą się = plural verb
• chcą = plural verb

This agreement works much like English children learn / children want.

A rough English-friendly guide is:

DJEH-chee OO-chon shyeh al-fa-BEH-too, bo htson LEH-pyey CHY-tatch po POL-skoo

A few useful points:

• dzieci sounds roughly like DJEH-chee
• cz in czytać sounds like ch
• się is roughly shyeh
• ą in uczą and chcą is a nasal vowel; at the end of a word it is often heard somewhat like on or om, though not exactly

Also, Polish stress usually falls on the second-to-last syllable:

• DZIE-ci
• U-czą
• al-fa-BE-tu
• CZY-tać
• POL-sku

The basic order here is very natural:

• Dzieci uczą się alfabetu, bo chcą lepiej czytać po polsku.

Literally, it is:

• Children learn the alphabet, because they want better to read in Polish

But Polish word order is more flexible than English. You can move parts around for emphasis, although the version given is the most neutral and natural for a learner to copy.

So this sentence is a good model of standard, everyday Polish word order.