Moja partnerka niczego nie kupiła na wyprzedaży, bo wszystko było za drogie.

Because partnerka is a feminine noun, and the possessive adjective my has to agree with it in gender, number, and case.

• mój = masculine singular
• moja = feminine singular
• moje = neuter singular

So:

• moja partnerka = my partner / my girlfriend
• mój partner = my male partner

Partnerka usually means female partner. Depending on context, it can mean:

• partner
• girlfriend
• sometimes female companion

It is a fairly neutral modern word. In many situations, it sounds less specific than dziewczyna and more adult or serious.

After negation in Polish, the direct object often changes to the genitive case. The verb here is negated with nie, so instead of a form like coś / coś kupiła, you get niczego nie kupiła.

Here:

• niczego = genitive form related to nic
• nie kupiła = did not buy

So niczego nie kupiła literally works like she bought nothing / she did not buy anything.

You may also hear nic nie kupiła in everyday speech, but niczego nie kupiła is very standard and grammatically clear.

Yes, and that is normal in Polish.

Polish regularly uses negative concord, which means multiple negative words appear together in one sentence:

• niczego nie kupiła = she bought nothing
• nikt nic nie wie = nobody knows anything
• nigdy tam nie chodzę = I never go there

In English, standard usage usually avoids this kind of double negative, but in Polish it is required.

Kupiła is the past tense, feminine singular form of kupić (to buy).

Polish past tense agrees with the subject’s gender:

• kupił = he bought
• kupiła = she bought
• kupiło = it bought
• kupili / kupiły = they bought

Since partnerka is feminine, the verb must be kupiła.

Because kupić is perfective, and it focuses on a completed result: to buy / to have bought.

• kupiła suggests a completed action: she ended up buying nothing
• kupowała is imperfective and would focus more on the process or repeated action

In this sentence, the point is the result: she didn’t buy anything, so kupiła is the natural choice.

It is genitive singular.

This happens because with many negated verbs, what would normally be the direct object shifts into the genitive.

So:

• affirmative idea: kupiła coś = she bought something
• negative: nie kupiła niczego = she bought nothing / she didn’t buy anything

Because the expression na wyprzedaży means at the sale or in the sale.

The preposition na here takes the locative case, and wyprzedaż changes like this:

• nominative: wyprzedaż
• locative: wyprzedaży

So:

• na wyprzedaży = at the sale / during the sale

This is a fixed and very common expression.

Yes, depending on context, it can be translated as:

• at the sale
• in the sale
• on sale

But grammatically, in this sentence it is literally more like at/in the sale. The exact English version depends on what sounds most natural in context.

Both can mean because, but they differ slightly in style.

• bo = very common, natural, conversational
• ponieważ = more formal or written
• gdyż = even more formal/bookish in many contexts

So:

• ..., bo wszystko było za drogie. sounds natural and everyday.
• ..., ponieważ wszystko było za drogie. is also correct, but a bit more formal.

Because wszystko means everything, and grammatically it behaves as a singular neuter word.

That is why the verb is also singular neuter:

• wszystko było = everything was

By contrast:

• wszystkie rzeczy były drogie = all the things were expensive

So:

• wszystko = everything, singular neuter
• wszystkie = all, used with plural nouns

It does look confusing, because drogie can be either:

• neuter singular
• or non-masculine-personal plural

Here it is neuter singular, because it agrees with wszystko.

Compare:

• to jest drogie = this is expensive
• wszystko było za drogie = everything was too expensive

So even though drogie can also be a plural form, in this sentence it is singular neuter.

Za drogie means too expensive.

In Polish, za before an adjective or adverb often means too in the sense of excessively:

• za drogie = too expensive
• za duże = too big
• za późno = too late

So:

• wszystko było za drogie = everything was too expensive

Yes, Polish word order is more flexible than English, because case endings show grammatical roles.

The original sentence is neutral and natural:

• Moja partnerka niczego nie kupiła na wyprzedaży, bo wszystko było za drogie.

But you could also move parts around for emphasis, for example:

• Na wyprzedaży moja partnerka niczego nie kupiła...
• Moja partnerka na wyprzedaży niczego nie kupiła...

These all mean roughly the same thing, but the emphasis changes slightly. The original version sounds very standard.

A few words may be tricky:

• niczego ≈ nee-CHEH-go
• kupiła ≈ koo-PEE-wa
• wyprzedaży ≈ vih-psheh-DAH-zhih
• drogie ≈ DRO-gye

A few helpful points:

• cz sounds roughly like ch in chocolate
• ż sounds like the s in measure
• ł sounds like English w
• rz usually sounds like ż

So wyprzedaży contains several sounds that English speakers often need to practise slowly.

You can understand it word by word, but a fully literal translation may sound unnatural in English.

Roughly:

• Moja partnerka = my partner
• niczego nie kupiła = bought nothing / didn’t buy anything
• na wyprzedaży = at the sale / in the sale
• bo = because
• wszystko było za drogie = everything was too expensive

Natural English versions would be:

• My partner didn’t buy anything in the sale because everything was too expensive.
• My partner bought nothing at the sale because everything was too expensive.

It is neutral everyday Polish.

Nothing in it is especially slangy or especially formal:

• moja partnerka is neutral
• niczego nie kupiła is standard grammar
• bo is common spoken/written language
• na wyprzedaży is a normal everyday phrase

So this is a very natural sentence to learn from.