Właściwie nie wiem, gdzie położyłam klucze do piwnicy.

Here właściwie does not mean properly in a literal sense. In this sentence it works more like actually, really, to be honest, or come to think of it. It makes the sentence sound more natural and conversational.

So Właściwie nie wiem... is something like Actually, I don’t know... or To be honest, I don’t know...

Polish often leaves out subject pronouns when they are clear from the verb form.

• wiem already means I know
• położyłam already means I put, said by a female speaker

So there is no need to add ja unless you want emphasis or contrast.

For example:

• Ja nie wiem = I don’t know with extra emphasis on I
• Nie wiem = the normal neutral version

Because in Polish, nie is usually written as a separate word with finite verbs.

So you write:

• nie wiem = I don’t know
• nie mam = I don’t have
• nie idę = I’m not going

That is the standard rule here.

Because Polish past tense agrees with the speaker’s gender.

• położyłam = I put, said by a woman
• położyłem = I put, said by a man

So this sentence is being said by a female speaker. If a male speaker said it, it would be:

Właściwie nie wiem, gdzie położyłem klucze do piwnicy.

This is a question of aspect.

• położyć is perfective
• kłaść is imperfective

In this sentence, the speaker is thinking about one completed action: Where did I put the keys? That is why Polish uses the perfective past form położyłam.

If you used kładłam, it would sound more like an ongoing, repeated, or unfinished action, which does not fit as well here.

So:

• gdzie położyłam klucze = where I put the keys
• gdzie kładłam klucze = where I was putting / used to put the keys

Klucze is in the accusative plural, because it is the direct object of położyłam.

The full idea is:

• położyłam co? = what did I put?
• klucze = the keys

A useful detail: klucz is a masculine inanimate noun, and for this type of noun, the nominative plural and accusative plural often look the same.

So klucze can be both:

• nominative plural: keys
• accusative plural: keys as a direct object

Piwnicy is in the genitive singular, because the preposition do requires the genitive.

So:

• piwnica = basement, cellar
• do piwnicy = to/for the basement, with piwnicy in the genitive

In this sentence, do piwnicy describes what kind of keys they are:

• klucze do piwnicy = keys to the basement / basement keys

This is a common Polish pattern:

• klucz do drzwi = key to the door
• klucz do mieszkania = key to the apartment

So do here does not show movement. It helps link the keys to what they open.

Yes, in everyday Polish you may also hear klucze od piwnicy. Both patterns exist.

Very roughly:

• klucze do piwnicy focuses on keys to/for the basement
• klucze od piwnicy often sounds like the basement keys, meaning the keys belonging to that place or lock

In many situations, the difference is small, and native speakers may use both. The version in your sentence, klucze do piwnicy, is completely normal.

Because gdzie położyłam klucze do piwnicy is a subordinate clause.

The main clause is:

• Właściwie nie wiem = Actually, I don’t know

Then comes the embedded clause:

• gdzie położyłam klucze do piwnicy = where I put the basement keys

In Polish, subordinate clauses are normally separated by a comma, so the comma is required here.

No, Polish word order is more flexible than English, although this version is very natural and neutral.

This order:

Właściwie nie wiem, gdzie położyłam klucze do piwnicy.

sounds like a normal everyday sentence.

You could move things around for emphasis, for example:

• Nie wiem właściwie, gdzie położyłam klucze do piwnicy.
• Klucze do piwnicy właściwie nie wiem, gdzie położyłam.

These are possible, but they change the rhythm or emphasis. The original version is the most straightforward.

A few helpful pronunciation points:

• właściwie ≈ vwash-CHEE-vyeh
• położyłam ≈ po-wo-ZHI-wam
• klucze ≈ KLOO-cheh
• piwnicy ≈ peev-NEE-tsih

A few sound details:

• ł sounds like English w
• ś is a soft sh sound
• ż in położyłam sounds like the s in measure
• cz sounds like ch in church

Stress in Polish is usually on the second-to-last syllable, so:

• wła-ŚCI-wie
• po-ło-ŻY-łam
• KLU-cze
• piw-NI-cy