W weekend opiekuję się psem sąsiadki, kiedy ona jedzie do Krakowa.

Because opiekować się requires the instrumental case.

• pies = nominative, the basic dictionary form: dog
• psem = instrumental: with/by means of a dog, but here just the form required after opiekuję się

So:

• opiekuję się psem = I take care of the dog

This is something you simply have to learn together with the verb:

• opiekować się + instrumental

Because sąsiadki is in the genitive case, showing possession.

• sąsiadka = the female neighbor
• pies sąsiadki = the neighbor’s dog
• psem sąsiadki = the neighbor’s dog in a structure where pies has already changed case

So the phrase means:

• psem sąsiadki = my female neighbor’s dog

If the neighbor were male, you would get:

• psem sąsiada = the male neighbor’s dog

Opiekuję się means I take care of, I look after, or I care for.

It comes from the verb:

• opiekować się = to take care of / to look after

The form opiekuję się is:

• 1st person singular
• present tense
• so literally: I take care of / I am taking care of

In Polish, the present tense can often cover both English I take care of and I am taking care of, depending on context.

Because opiekować się is a verb that normally includes się. You learn it as one unit:

• opiekować się kimś/czymś = to take care of someone/something

Here się is not optional. You cannot normally say:

• opiekuję psem ❌

You need:

• opiekuję się psem ✅

Many Polish verbs work this way, and English speakers often just need to memorize them as fixed combinations.

By itself, w weekend is somewhat context-dependent and also a bit colloquial.

It can suggest:

• at the weekend / on the weekend
• sometimes this weekend
• sometimes a general weekend-time setting

If you want to be clearer:

• w ten weekend = this weekend
• w weekendy = on weekends / every weekend

So if the meaning is habitual, many learners would expect:

• W weekendy opiekuję się psem sąsiadki...

If it is about one specific upcoming weekend, then:

• W ten weekend opiekuję się psem sąsiadki...

Yes, it is very common in everyday Polish, especially in speech.

However, depending on style, some people may prefer more explicit forms like:

• w weekendy = on weekends
• w ten weekend = this weekend
• w ciągu weekendu = during the weekend in some contexts

So w weekend is normal and understandable, but it can feel a little colloquial or slightly less precise than other options.

Because kiedy ona jedzie do Krakowa is a subordinate clause.

Polish punctuation usually places a comma before conjunctions like:

• kiedy = when
• że = that
• bo = because
• jeśli = if

So:

• Opiekuję się psem sąsiadki, kiedy ona jedzie do Krakowa.

That comma is standard.

Yes, it can often be omitted.

Polish usually drops subject pronouns when the verb already makes the subject clear. So this is also natural:

• W weekend opiekuję się psem sąsiadki, kiedy jedzie do Krakowa.

Including ona can add:

• slight emphasis
• contrast
• clarity

For example, it may help show that she is the one going to Krakow, not someone else.

So:

• kiedy ona jedzie do Krakowa = a bit more explicit
• kiedy jedzie do Krakowa = more neutral and often more natural

Because jechać is used for traveling by vehicle or for a journey over distance, while iść means to go on foot.

• jedzie do Krakowa = she is going/traveling to Krakow
• idzie do Krakowa would sound like she is literally walking there

Since going to another city usually involves transport, jechać is the normal choice.

Because do + genitive is used to express movement to a place.

• do Krakowa = to Krakow
• w Krakowie = in Krakow
• na Kraków is not used this way for cities

So:

• jedzie do Krakowa = she is going to Krakow
• jest w Krakowie = she is in Krakow

Also note the case change:

• Kraków → do Krakowa

It could be understood either way, depending on context, but the sentence as written is a little ambiguous.

• opiekuję się can mean I take care of or I am taking care of
• w weekend can mean this weekend or more generally at the weekend

So the sentence could mean:

• a one-time situation: This weekend I’m taking care of my neighbor’s dog when she goes to Krakow
• or a repeated pattern, though for that w weekendy would usually be clearer

If you want a clearly repeated meaning, Polish would often use:

• W weekendy opiekuję się psem sąsiadki, kiedy ona jeździ do Krakowa.

Notice that a repeated trip would also often use jeździ instead of jedzie.

This is a question of aspect / repeatedness.

• jedzie = is going / goes in a specific instance
• jeździ = goes regularly / travels repeatedly

So:

• kiedy ona jedzie do Krakowa = when she goes / is going to Krakow on a particular occasion
• kiedy ona jeździ do Krakowa = when she goes to Krakow regularly

If the whole sentence is meant as a habit, many Polish speakers might prefer:

• W weekendy opiekuję się psem sąsiadki, kiedy ona jeździ do Krakowa.

Yes. Polish word order is more flexible than English, though not completely free.

The original sentence is natural:

• W weekend opiekuję się psem sąsiadki, kiedy ona jedzie do Krakowa.

You could also say:

• Kiedy ona jedzie do Krakowa, w weekend opiekuję się psem sąsiadki.
• Psem sąsiadki opiekuję się w weekend, kiedy ona jedzie do Krakowa.

But different word orders change the emphasis. The original is probably the most neutral for a learner.

Yes. Sąsiadka is specifically a female neighbor, so sąsiadki means of the female neighbor.

Compare:

• sąsiadka = female neighbor
• sąsiad = male neighbor

So:

• psem sąsiadki = the female neighbor’s dog
• psem sąsiada = the male neighbor’s dog

If English just says neighbor, Polish often forces you to choose male or female.

Yes, but many speakers might choose a slightly more precise version depending on the intended meaning.

Possible natural alternatives:

• W ten weekend opiekuję się psem sąsiadki, kiedy ona jedzie do Krakowa.
  = clearly this weekend

• W weekendy opiekuję się psem sąsiadki, kiedy ona jeździ do Krakowa.
  = clearly on weekends / habitually

So the original sentence is understandable and natural enough, but in real conversation Polish speakers often make the time meaning more explicit.