W wakacje chodzę spać później niż w tygodniu.

Yes. Wakacje is normally a plural-only noun in Polish, meaning summer holidays / vacation.

So Polish says:

• wakacje są długie = the summer holidays are long
• w wakacje = during the summer holidays

This is similar to English holidays, though English also has singular vacation, while standard Polish usually uses plural wakacje for this idea.

Both can be possible, but they are not exactly the same in feel.

• w wakacje = during the holiday period / in the summer holidays
• na wakacjach = on holiday / away on vacation

In your sentence, w wakacje chodzę spać później sounds like a general statement about your routine during the summer break.

By contrast:

• Na wakacjach chodzę spać później often sounds more like when I’m on vacation.

So w wakacje is a very natural choice when talking about habits in the holiday season as a time period.

Chodzić spać is a standard Polish expression meaning to go to bed / go to sleep as a repeated habit.

So:

• chodzę spać o 11 = I go to bed at 11
• dzieci chodzą spać wcześnie = children go to bed early

It does not mean that you are literally walking somewhere in this sentence. This is just how Polish expresses the idea of going to bed.

Because chodzę expresses a habitual / repeated action, while idę usually refers to one specific occasion.

Compare:

• Chodzę spać późno. = I go to bed late / I tend to go to bed late
• Idę spać. = I’m going to bed now

In your sentence, the speaker is describing a regular pattern:

• During the holidays, I go to bed later than during the week.

So chodzę is exactly what you want.

Because Polish often drops subject pronouns when the verb ending already shows who the subject is.

Here:

• chodzę = I go / I am going habitually

The ending -ę already tells us the subject is I, so ja is unnecessary.

You could say Ja chodzę spać później niż w tygodniu, but that would add emphasis, for example if you are contrasting yourself with someone else.

Because the sentence is making a comparison.

• późno = late
• później = later

Since the sentence says later than during the week, Polish uses the comparative form:

• później niż = later than

Compare:

• Chodzę spać późno. = I go to bed late.
• Chodzę spać później niż ty. = I go to bed later than you.

Niż means than in comparisons.

So:

• później niż = later than
• większy niż = bigger than
• szybciej niż = faster than

In your sentence:

• później niż w tygodniu = later than during the week

Here w tygodniu means during the week, often with the sense of on weekdays / in the normal work-or-school week.

So the contrast is:

• w wakacje = during the holidays
• w tygodniu = during the regular week / on weekdays

In this sentence, it does not mean in a week as in within one week. It means during the week as a time period.

This is a very good question, because Polish time expressions with w are not all built the same way.

You will meet several patterns, for example:

• w poniedziałek = on Monday
• w weekend = at the weekend
• w tygodniu = during the week
• w wakacje = during the holidays

So although the preposition is the same, the noun form after it can vary depending on the expression. In practice, learners usually have to learn these as common time phrases.

In your sentence:

• w tygodniu uses the form tygodniu (locative singular)
• w wakacje looks the same as the dictionary form because wakacje is plural and this time expression is fixed that way

The most helpful approach is: learn whole chunks such as w tygodniu, w wakacje, w weekend, w poniedziałek.

Yes. Polish word order is more flexible than English, though different orders can shift the emphasis.

Your sentence:

• W wakacje chodzę spać później niż w tygodniu.

A few other possible versions:

• Chodzę spać później w wakacje niż w tygodniu.
• Później chodzę spać w wakacje niż w tygodniu. (less neutral, more marked)

The original version is very natural because it puts the time frame w wakacje first, setting the scene right away.

It describes a general habit.

That comes mainly from:

• chodzę = habitual/repeated
• the general time expressions w wakacje and w tygodniu

So the sentence means that, as a rule, the speaker’s bedtime is later during the holidays than during the regular week.

If you wanted a one-time meaning, Polish would usually use different wording, for example something with idę spać for a specific moment:

• Dzisiaj idę spać później niż zwykle. = Today I’m going to bed later than usual.