W maju park wygląda pięknie, bo wszystko jest zielone.

Because the preposition w often requires the locative case when it means in.

• maj = May
• w maju = in May

So maj changes to maju in the locative.

This is very common with names of months after w:

• w styczniu = in January
• w lutym = in February
• w maju = in May

Polish does not use articles like a or the.

So:

• park can mean a park or the park
• the exact meaning depends on context

In this sentence, English naturally uses the park, but Polish simply says park.

Wyglądać means to look / to appear.

So:

• park wygląda pięknie = the park looks beautiful

This is different from:

• park jest piękny = the park is beautiful

Both are possible, but they are not exactly the same:

• jest piękny describes a quality more directly
• wygląda pięknie emphasizes how it appears at that moment

In this sentence, wygląda pięknie sounds very natural because the speaker is talking about how the park looks in May.

Because wyglądać is usually followed by an adverb, not an adjective, in this kind of sentence.

• piękny = beautiful (adjective)
• pięknie = beautifully / beautiful in appearance (adverb)

So:

• park jest piękny = the park is beautiful
• park wygląda pięknie = the park looks beautiful

This is similar to English, where we often say looks beautiful, even though Polish uses the adverb form pięknie.

Because in Polish, bo introduces a new clause, and it is normally preceded by a comma.

• bo = because

So the sentence is split like this:

• W maju park wygląda pięknie,
• bo wszystko jest zielone.

This comma is standard Polish punctuation.

Bo means because.

It is very common in everyday speech and writing. It sounds natural and conversational.

You could also use:

• ponieważ = because / since
• gdyż = because, as

For example:

• W maju park wygląda pięknie, ponieważ wszystko jest zielone.

That is also correct, but bo is simpler and more common in everyday language.

Because wszystko is grammatically treated as singular and usually neuter.

So it takes:

• jest = is
• zielone = green (neuter singular)

Even though wszystko refers to many things in meaning, grammatically it behaves like a singular word:

• wszystko jest dobre = everything is good
• wszystko jest gotowe = everything is ready
• wszystko jest zielone = everything is green

Because zielone agrees with wszystko, which is treated as neuter singular.

Compare:

• ten park jest zielony = this park is green
  
  • park is masculine, so zielony
• ta trawa jest zielona = this grass is green
  
  • trawa is feminine, so zielona
• wszystko jest zielone = everything is green
  
  • wszystko is neuter, so zielone

So the ending changes to match the grammatical gender and number of the subject.

Wygląda is:

• 3rd person singular
• present tense
• from the verb wyglądać = to look / to appear

It matches park, which is singular:

• park wygląda = the park looks

A few related forms:

• wyglądam = I look
• wyglądasz = you look
• wygląda = he/she/it looks
• wyglądamy = we look
• wyglądają = they look

Yes, Polish word order is relatively flexible.

The neutral order here is:

• W maju park wygląda pięknie, bo wszystko jest zielone.

But you could also say:

• Park wygląda pięknie w maju, bo wszystko jest zielone.

Both are correct. The difference is mainly in emphasis:

• W maju at the beginning emphasizes the time
• Park at the beginning emphasizes the park

The original sentence sounds very natural.

It can mean either, depending on context.

• W maju park wygląda pięknie can mean:
  • In May, the park looks beautiful in general
  • or This May, the park looks beautiful, if the context makes that clear

Polish often leaves that kind of distinction to context instead of adding extra words.

A rough pronunciation guide:

• wygląda ≈ vih-GWON-da

A few notes:

• wy sounds roughly like vih
• glą contains ą, a nasal vowel
• before d, ą is often pronounced somewhat like on

So in normal speech, wygląda may sound close to vygwon-da.

You do not need to make it exactly like English on, but that approximation helps at first.

Yes, that is grammatically correct.

It would mean:

• In May, the park is beautiful, because everything is green.

But the original:

• park wygląda pięknie

focuses more on how the park looks. That sounds especially natural when talking about seasonal appearance.

So both are correct, but the original sentence is a little more vivid and descriptive.