W grudniu kupujemy prezenty i pieczemy ciastka z cynamonem.

Because after the preposition w meaning in, Polish uses the locative case for months.

The basic form is grudzień = December.
After w, it changes to grudniu:

• grudzień → w grudniu

So w grudniu means in December.

This is very common with months:

• w styczniu = in January
• w lutym = in February
• w maju = in May

So the learner should think: w + month = locative form.

Here w means in.

So:

• w grudniu = in December

Be careful, because w can also mean inside / at / in, depending on context. But with months, it is usually just in.

In Polish, subject pronouns are often omitted because the verb ending already shows who is doing the action.

Here:

• kupujemy = we buy / we are buying
• pieczemy = we bake / we are baking

The ending -my tells you the subject is we.

So my is not necessary. You could say:

• My kupujemy prezenty i pieczemy ciastka z cynamonem.

But that usually adds emphasis, like we in particular.

Because kupujemy is the 1st person plural form of the verb kupować = to buy.

Pattern:

• kupuję = I buy
• kupujesz = you buy
• kupuje = he/she/it buys
• kupujemy = we buy
• kupujecie = you all buy
• kupują = they buy

So the ending -emy / -my is a strong clue that the subject is we.

Pieczemy is we bake, from the verb piec = to bake.

Its forms are a bit less regular-looking than some other verbs, so it is worth memorizing:

• piekę = I bake
• pieczesz = you bake
• piecze = he/she/it bakes
• pieczemy = we bake

So in the sentence, pieczemy ciastka means we bake cookies.

In Polish, the present tense is often used for habitual or general repeated actions, just like in English.

So kupujemy and pieczemy can mean:

• we buy / we bake in general
• we usually buy / we usually bake
• we buy and bake in December as a regular custom

It does not have to mean right now at this moment. It can describe something people typically do.

Prezenty is the plural of prezent = gift / present.

Here it is the direct object of kupujemy (we buy), so you might expect a special accusative form. But for many inanimate non-masculine-personal plural nouns, the accusative plural looks the same as the nominative plural.

So:

• nominative plural: prezenty
• accusative plural: prezenty

That is why the sentence uses kupujemy prezenty.

Ciastka is the plural of ciastko.

In everyday Polish, ciastko / ciastka usually means:

• cookie / cookies
• sometimes small cakes / pastries, depending on context

In this sentence, ciastka z cynamonem is most naturally understood as cinnamon cookies.

Just like prezenty, ciastka here is the object of the verb, and its accusative plural is the same as its nominative plural.

Because the preposition z meaning with requires the instrumental case.

The basic form is:

• cynamon = cinnamon

After z meaning with, it becomes:

• z cynamonem = with cinnamon

So the ending -em shows the instrumental singular.

More examples:

• z mlekiem = with milk
• z cukrem = with sugar
• z przyjacielem = with a friend

No. Z can mean different things depending on the case that follows it.

Most importantly:

• z + instrumental = with
• z + genitive = from / off

In this sentence:

• z cynamonem = with cinnamon

So here it is the with meaning, and that is why the noun is in the instrumental case.

Starting with W grudniu puts the time phrase first: In December...

This is very natural in Polish. Polish word order is more flexible than English, and speakers often move elements to the front for emphasis or topic-setting.

So:

• W grudniu kupujemy prezenty i pieczemy ciastka z cynamonem.

feels like:

• As for December / In December, we buy presents and bake cinnamon cookies.

You could also say:

• Kupujemy prezenty i pieczemy ciastka z cynamonem w grudniu.

That is grammatical too, but it sounds a bit less natural as a neutral statement about what happens in December.

Because Polish does not have articles like a, an, or the.

So nouns appear without them:

• prezenty = presents / the presents / some presents
• ciastka = cookies / the cookies / some cookies

The exact meaning depends on context, not on an article.

That is one reason Polish can feel more compact than English.

Not in the same way, if you want this general habitual meaning.

The sentence uses imperfective verbs:

• kupować → kupujemy
• piec → pieczemy

These are appropriate for repeated, customary actions.

If you used perfective verbs, the meaning would change toward a completed future action, for example:

• W grudniu kupimy prezenty i upieczemy ciastka z cynamonem.

This means more like:

• In December we will buy presents and bake cinnamon cookies.

So the original sentence sounds like a habit or tradition, while the perfective version sounds like a planned completed event in the future.

Yes. I is the standard Polish word for and.

So:

• prezenty i pieczemy... = presents and we bake...

It simply links the two verb phrases:

• kupujemy prezenty
• pieczemy ciastka z cynamonem

A rough guide:

• grudniu ≈ GROOD-nyoo
• pieczemy ≈ pye-CHE-my

A few useful pronunciation notes:

• dzi / dni / niu types of combinations often create a soft ny-like sound before u
• cz sounds like ch in chocolate
• pie at the start of pieczemy is closer to pye, not like English pee

So:

• W grudniu ≈ vgrood-nyoo
• pieczemy ≈ pye-che-my

It can be understood either way, depending on context.

Without extra context, it most naturally means:

• we as a group are describing our December habit/tradition

But in some contexts, Polish we can also sound more general, like we people / we as a culture.

So this sentence could describe:

• a family tradition
• what people in general tend to do around Christmas time
• a shared custom in a community

Context tells you which one is intended.