Gdy na podłodze jest dużo kurzu, najpierw zamiatam miotłą, a potem biorę mop.

Here gdy means when.

In this sentence, gdy and kiedy are very close in meaning, and you could say:

Kiedy na podłodze jest dużo kurzu...

without changing the basic meaning.

A few nuances:

• gdy can sound a bit more formal or written
• kiedy is very common in everyday speech
• in sentences like this, both can also feel like whenever

So the whole beginning can be understood as:

• When there is a lot of dust on the floor...
• or Whenever there is a lot of dust on the floor...

Because na is followed by different cases depending on the meaning.

Here it means location: on the floor, so Polish uses the locative case.

• basic form: podłoga = floor
• locative after na: na podłodze = on the floor

Compare:

• na podłodze = on the floor (location)
• na podłogę = onto the floor (movement toward a surface)

So in this sentence, the dust is already there, so location is meant, not movement.

That is the normal locative singular form of podłoga.

Polish nouns often change their endings in cases, and sometimes the stem changes a little too. Here:

• podłoga → podłodze

This kind of consonant change is common in Polish declension. For a learner, the important thing is to memorize:

• podłoga = floor
• na podłodze = on the floor

Because dużo usually requires the genitive.

So:

• kurz = dust
• kurzu = of dust / dust in the genitive

After quantity words like dużo, mało, trochę, Polish very often uses the genitive:

• dużo wody = a lot of water
• mało czasu = little time
• trochę mleka = a little milk
• dużo kurzu = a lot of dust

Since dust is treated as an uncountable substance, Polish uses the singular genitive: kurzu.

Because Polish is expressing existence: there is a lot of dust on the floor.

Literally, the structure is close to:

• On the floor is a lot of dust

So jest means is / there is here.

This is a very common Polish pattern:

• Na stole jest książka. = There is a book on the table.
• W pokoju jest cicho. = It is quiet in the room.
• Na podłodze jest dużo kurzu. = There is a lot of dust on the floor.

Because Polish usually drops subject pronouns when they are clear from the verb ending.

• zamiatam = I sweep
• biorę = I take

So ja is not necessary.

You could say:

• Ja najpierw zamiatam...

but that would usually add emphasis, something like:

• I sweep first...

In neutral sentences, Polish normally leaves ja out.

Zamiatam is the 1st person singular present tense of zamiatać.

Formally, it is present tense, but in this sentence it expresses a habitual / repeated action, not necessarily something happening at this exact moment.

So the meaning is more like:

• When there’s a lot of dust on the floor, I first sweep with a broom, then I take the mop.
• or Whenever there’s a lot of dust on the floor, I first sweep...

This is very common in both Polish and English: present tense can describe routine behavior.

Because miotłą is in the instrumental case.

Polish often uses the instrumental to show the tool or means used to do something.

• miotła = broom
• miotłą = with a broom

So:

• zamiatam miotłą = I sweep with a broom

Other examples:

• piszę długopisem = I write with a pen
• jadę autobusem = I go by bus
• kroję nożem = I cut with a knife

So the -ą ending here signals the instrumental singular of a feminine noun.

Miotła means broom.

In this sentence, zamiatam miotłą clearly means I sweep with a broom.

A szczotka is usually a brush, not a broom. So for floor-sweeping, miotła is the natural word here.

They mean:

• najpierw = first
• potem = then / afterward

So:

• najpierw zamiatam miotłą = first I sweep with a broom
• a potem biorę mop = and then I take the mop

They show the order of actions very clearly.

All of these are possible in some contexts, but a potem is very natural in Polish for linking one step to the next.

Here a does not necessarily mean a strong contrast. It often works like:

• and then
• while then
• and after that

So:

• najpierw..., a potem... = first..., and then...

This is a very common Polish pairing.

Biorę mop literally means I take the mop or I pick up the mop.

That sounds natural because the sentence is describing the sequence of cleaning actions:

1. first I sweep with a broom
2. then I take the mop

It focuses on the next step: reaching for the mop.

If you wanted to say the actual mopping action more explicitly, you could say something like:

• ...a potem myję podłogę mopem. = ...and then I wash the floor with a mop.
• ...a potem mopuję podłogę. = ...and then I mop the floor.

The given sentence is not wrong at all; it just highlights taking the mop as the next action.

It actually is in the accusative, but for this kind of noun the accusative looks the same as the basic form.

• basic form: mop
• accusative singular: mop

That happens because mop is a masculine inanimate noun. In Polish, masculine inanimate nouns often have:

• nominative = accusative

So:

• mam stół = I have a table
• widzę dom = I see a house
• biorę mop = I take a mop / the mop

The case is accusative because mop is the direct object of biorę, even though the form stays the same.

In practice, it is closer to whenever or when(ever this happens).

Because the sentence is about a repeated situation and a usual response, the meaning is:

• Whenever there is a lot of dust on the floor, I first sweep with a broom, then I take the mop.

English often uses simple when for this too, so when is also a perfectly fine translation.

Yes. Polish word order is fairly flexible, although some orders sound more natural than others.

The original sentence is very natural because it presents:

1. the condition
2. the sequence of actions

You could also hear variations like:

• Kiedy na podłodze jest dużo kurzu, najpierw zamiatam miotłą, a potem biorę mop.
• Najpierw zamiatam miotłą, a potem biorę mop, gdy na podłodze jest dużo kurzu.

But the original version is the clearest and most neutral.

There are two reasons.

1. Gdy na podłodze jest dużo kurzu is a subordinate clause, and in Polish such clauses are normally separated by a comma.

So you get:

• Gdy na podłodze jest dużo kurzu, ...

2. There is also a comma before a potem, because a joins two coordinated parts of the sentence:

• najpierw zamiatam miotłą, a potem biorę mop

So the punctuation is completely standard Polish punctuation.