We wtorek mam mniej spotkań niż w poniedziałek, więc mam więcej czasu na odpoczynek.

We is just a pronunciation-friendly variant of w. Polish often uses we before a difficult consonant cluster, and w wtorek is awkward to say because of the repeated w sound.

So:

• we wtorek = the normal, natural form
• w wtorek = grammatically understandable, but not standard/natural

The meaning does not change.

With days of the week, Polish uses w + accusative to mean on Monday, on Tuesday, etc.

So in this sentence:

• we wtorek
• w poniedziałek

both weekday nouns are in the accusative.

For masculine inanimate nouns like wtorek and poniedziałek, the accusative singular looks the same as the nominative singular, so there is no visible ending change. That is why poniedziałek stays poniedziałek.

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

The verb mam already means I have, so ja is not necessary.

• mam = I have
• ja mam = I have, but with extra emphasis, like I have

In a neutral sentence, Polish normally prefers just mam.

After quantity words like mniej and więcej, Polish usually puts the noun in the genitive.

Here, spotkanie is a countable noun, so after mniej it becomes genitive plural:

• singular: spotkanie
• nominative plural: spotkania
• genitive plural: spotkań

So:

• mniej spotkań = fewer meetings

This is a very common Polish pattern:

• więcej książek = more books
• mniej problemów = fewer problems
• więcej pytań = more questions

For the same reason: więcej requires the genitive.

But czas is usually treated here as an uncountable noun, so Polish uses the genitive singular:

• nominative: czas
• genitive: czasu

So:

• więcej czasu = more time

Compare:

• więcej czasu = more time
• więcej spotkań = more meetings

The first uses genitive singular because time is treated as a mass noun; the second uses genitive plural because meetings are countable.

Niż means than in comparisons.

So:

• mniej spotkań niż w poniedziałek = fewer meetings than on Monday

It is used after comparative words such as:

• mniej = less/fewer
• więcej = more
• lepiej = better
• gorzej = worse

Examples:

• więcej niż zwykle = more than usual
• lepiej niż wcześniej = better than earlier

Because Polish often leaves out repeated words when they are obvious from context.

So:

• mam mniej spotkań niż w poniedziałek
  is a shorter, natural version of:
• mam mniej spotkań niż mam w poniedziałek

The fuller version is possible, but it sounds more repetitive. Polish often prefers the shorter form when the meaning is clear.

Więc means so, therefore, or thus.

It connects the two ideas:

• fewer meetings
• as a result, more time to rest

The comma is standard in Polish before więc when it joins clauses like this.

So the structure is:

• clause 1, więc clause 2

This is similar to English punctuation in sentences like:

• I have fewer meetings, so I have more time.

Because Polish very often uses the pattern:

• czas na + noun

So:

• czas na odpoczynek = time for rest / time to rest

Here odpoczynek is a noun meaning rest.

A verbal version is also possible, for example:

• mam więcej czasu, żeby odpocząć = I have more time to rest

Both are correct, but czas na odpoczynek is a very natural and common Polish structure.

It is in the accusative.

The expression na odpoczynek uses na + accusative. In this kind of phrase, na often has the sense of for or for the purpose of.

So:

• czas na kawę = time for coffee
• czas na obiad = time for lunch
• czas na odpoczynek = time for rest

For odpoczynek, the accusative form happens to look the same as the nominative:

• nominative: odpoczynek
• accusative: odpoczynek

Yes. Polish word order is flexible, although some versions sound more natural in certain contexts.

The sentence begins with We wtorek because time expressions are often placed near the beginning of the sentence.

You could also say:

• Mam we wtorek mniej spotkań niż w poniedziałek, więc mam więcej czasu na odpoczynek.

That is also correct. The difference is mostly one of emphasis:

• We wtorek... emphasizes the time first
• Mam we wtorek... emphasizes the fact that I have fewer meetings

In Polish, days of the week are normally written with lowercase letters, unlike in English.

So Polish writes:

• poniedziałek
• wtorek
• środa

not Monday, Tuesday, Wednesday with capitals.

They are only capitalized at the beginning of a sentence or in special formatting.

You would usually use the plural:

• we wtorki = every Tuesday / on Tuesdays

So:

• We wtorek mam mniej spotkań... = On Tuesday / This Tuesday I have fewer meetings...
• We wtorki mam mniej spotkań... = On Tuesdays / Every Tuesday I have fewer meetings...

This is a very useful distinction:

• singular weekday = one specific day
• plural weekday = habitual/repeated action