Do końca lekcji zostało piętnaście minut, więc dzieci rysują szybciej.

Because the preposition do requires the genitive case.

• koniec = the end
• do końca = until the end / to the end

So after do, koniec changes to końca.

This is a very common pattern in Polish:

• do domu = to home
• do szkoły = to school
• do końca = until the end

Lekcji is also in the genitive case.

In do końca lekcji, the structure is basically:

• do
  • genitive
• końca lekcji = the end of the lesson

So:

• lekcja = lesson
• lekcji = of the lesson

This is similar to English the end of the lesson, where lesson depends on end.

This is one of the most common things learners notice in sentences with numbers.

In Polish, with numbers 5 and above, the phrase often behaves grammatically in a special way. Even though piętnaście minut refers to many minutes, the verb is usually put in neuter singular in past-tense existential-type sentences like this.

So Polish says:

• zostało pięć minut
• zostało dziesięć minut
• zostało piętnaście minut

not normally:

• zostały piętnaście minut

You can think of zostało piętnaście minut as something like:

• there remained fifteen minutes
• there were fifteen minutes left

The whole quantity is treated as one amount.

Because after numbers 5 and higher, the counted noun usually goes into the genitive plural.

So:

• jedna minuta = one minute
• dwie / trzy / cztery minuty = two / three / four minutes
• pięć minut = five minutes
• piętnaście minut = fifteen minutes

That is why minuta changes to minut here.

A useful pattern:

• 1 → nominative singular
• 2, 3, 4 → nominative plural-like form
• 5+ → genitive plural

Yes, basically — but in this sentence it works in a very natural Polish pattern meaning there were ... left or ... remained.

So:

• zostało piętnaście minut = fifteen minutes were left / there were fifteen minutes left

Polish often uses zostać in this way when talking about time, quantity, money, and so on:

• Zostało mi pięć złotych. = I have five złoty left.
• Zostało trochę kawy. = There is some coffee left.
• Zostało dziesięć minut. = There are ten minutes left.

Because Polish does not need a dummy subject like English there.

English says:

• There are fifteen minutes left

Polish simply says:

• Zostało piętnaście minut

This is very normal. Polish often leaves out things that English must include.

Because dzieci is the nominative plural form of dziecko.

• dziecko = child
• dzieci = children

It is an irregular noun, so the plural does not look like the singular.

Here dzieci is the subject of rysują, so it must be in the nominative:

• dzieci rysują = the children are drawing

Rysują is the 3rd person plural present tense of rysować.

• rysować = to draw
• rysuję = I draw / am drawing
• rysujesz = you draw
• rysuje = he/she/it draws
• rysujemy = we draw
• rysujecie = you all draw
• rysują = they draw / are drawing

Because the subject is dzieci = children, Polish uses the they form:

• dzieci rysują

Because Polish present tense often covers both:

• they draw
• they are drawing

So dzieci rysują can mean:

• the children draw
• the children are drawing

The context tells you which one is meant. In this sentence, it clearly means something happening now, so English naturally uses are drawing.

Because szybciej is the comparative adverb: faster.

• szybko = quickly
• szybciej = more quickly / faster

The sentence implies a comparison:

• they are drawing faster now, because little time is left

So:

• dzieci rysują szybciej = the children are drawing faster

It is the comparative form of szybko.

• szybko = quickly
• szybciej = faster / more quickly
• najszybciej = fastest / most quickly

This is a common comparative pattern in Polish adverbs and adjectives, though the exact form is not always fully predictable.

Compare:

• wolno → wolniej = slowly → more slowly
• ładnie → ładniej = nicely → more nicely
• szybko → szybciej = quickly → faster

Because więc is a coordinating conjunction meaning so, and in Polish it is normally preceded by a comma when it connects clauses.

So:

• Do końca lekcji zostało piętnaście minut, więc dzieci rysują szybciej.

This is standard punctuation.

Yes, Polish word order is fairly flexible, but different orders sound more or less natural depending on emphasis.

The given sentence is very natural:

• Do końca lekcji zostało piętnaście minut, więc dzieci rysują szybciej.

You might also hear:

• Zostało piętnaście minut do końca lekcji...
• Piętnaście minut zostało do końca lekcji...

But these do not all feel exactly the same in rhythm or emphasis.

The original version is natural because it starts with the time-frame:

• Do końca lekcji = until the end of the lesson

That sets the situation before giving the amount of time left.

Sometimes learners try to use jest because English says there are fifteen minutes left, but in Polish zostało is much more natural here.

• jest piętnaście minut usually just means it is fifteen minutes in some context, or sounds incomplete/unnatural here
• zostało piętnaście minut clearly means fifteen minutes are left

So for remaining time, zostało is the normal choice.

It often translates as either lesson or class, depending on context.

In this sentence:

• do końca lekcji could be understood as until the end of the lesson or until the end of class

Both are natural translations in English. The Polish word itself is completely normal here.

Usually not in a sentence like this, unless the context already makes it extremely obvious.

You normally say:

• zostało piętnaście minut

not just:

• zostało piętnaście

The noun minut tells you what the number refers to. Without it, the sentence sounds incomplete in most situations.

Because the sentence expresses cause and result:

• Do końca lekcji zostało piętnaście minut = only fifteen minutes are left
• więc dzieci rysują szybciej = so the children are drawing faster

This is a very common Polish pattern:

• statement 1
• więc
• result

It works much like English so.