W sobotę pracuję do południa, a potem odpoczywam w domu.

Because sobota changes here to the accusative singular: sobotę.

In Polish, when you talk about on a particular day of the week, you very often use w + accusative:

• w sobotę = on Saturday
• w niedzielę = on Sunday
• w środę = on Wednesday

So w sobotę is the normal way to say on Saturday.

In Polish, names of days of the week are normally written with a lowercase letter:

• sobota
• niedziela
• poniedziałek

So w sobotę is correct. Polish does not capitalize weekdays the way English does.

Pracuję is the 1st person singular present tense of pracować = to work.

So it means I work or I am working, depending on context.

The ending -ę already tells you the subject is I, which is why Polish does not need ja here.

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

• pracuję already means I work
• odpoczywam already means I rest / I relax

Adding ja is possible, but it usually adds emphasis, like I specifically.

So the sentence sounds more natural without it: W sobotę pracuję do południa...

Do południa means until noon or before noon.

Here:

• do = until / up to
• południa is the form of południe used after do

So: pracuję do południa = I work until noon

A useful contrast is:

• do południa = before noon / until noon
• po południu = in the afternoon / after noon

Those two are easy to confuse, so they are worth learning together.

Because the preposition do requires the genitive case.

The base form is:

• południe = noon

After do, it changes to:

• do południa = until noon

So this is a case ending change, not a different word.

Potem means then, afterwards, or later.

The conjunction a often links two parts of a sentence when there is a natural shift from one action to another. In this sentence, it sounds very natural:

• pracuję do południa, a potem odpoczywam w domu
• I work until noon, and then I relax at home

You might think of a here as something between and and and then.

I potem is possible in some contexts, but a potem is the more natural choice here.

Because in Polish, a comma is normally used before conjunctions like a, ale, bo, więc when they join clauses.

So this punctuation is standard:

W sobotę pracuję do południa, a potem odpoczywam w domu.

Even if English punctuation sometimes feels different, in Polish this comma is expected.

Because w means in or at, and when it shows location, it takes the locative case.

The base form is:

• dom = house / home

After w, it becomes:

• w domu = at home / in the house

So: odpoczywam w domu = I relax at home

This is an important distinction:

• w domu = at home / in the house → location
• do domu = to home / homeward → movement toward home

So:

• Odpoczywam w domu = I relax at home
• Idę do domu = I’m going home

In your sentence, the speaker is already at home while relaxing, so w domu is correct.

In Polish, the present tense can be used for:

• something happening now
• a habitual action
• a planned or scheduled action, depending on context

So W sobotę pracuję do południa can mean something like:

• On Saturday I work until noon
• This Saturday I’m working until noon
• On Saturdays I work until noon, if the context makes it clear

Polish often relies on context more than English does here.

It can mean either, depending on context.

• W sobotę pracuję... can mean This Saturday I’m working...
• It can also sound like a general Saturday routine in the right context

If you want to make the habitual meaning clearer, Polish often says:

• W soboty pracuję do południa... = On Saturdays I work until noon...
• W każdą sobotę pracuję do południa... = Every Saturday I work until noon...

So the original sentence is natural, but context decides whether it is one Saturday or a repeated habit.

Yes. Polish word order is fairly flexible, although the original version is very natural and neutral.

For example, these are also possible:

• W sobotę do południa pracuję, a potem odpoczywam w domu.
• W sobotę pracuję do południa, a w domu potem odpoczywam.
  This is possible, but less natural in everyday speech.

Changing the word order usually changes emphasis, not the basic meaning. The original sentence is a good standard model to learn.