wǒ xiǎng qù gōngyuán, búguò wǒ jīntiān yào shàngbān.

This is because of a very common pronunciation rule in Mandarin called tone sandhi.

• 不 is normally fourth tone: bù
• But when 不 comes before another fourth-tone syllable, it changes to second tone
• 过 in 不过 is fourth tone: guò
• So 不 + 过 becomes búguò

You will see this a lot:

• 不是 → bú shì
• 不要 → bú yào
• 不去 → bú qù

In writing, it is still written as 不. Only the pronunciation changes.

In this sentence, 想 means would like to / want to.

So:

• 我想去公园 = I want to go to the park

This is different from English, where think and want are completely different words. In Chinese, 想 can have more than one meaning depending on context:

• 我想去公园 = I want to go to the park
• 我想一想 = I’ll think about it
• 我想他今天不来 = I think he isn’t coming today

Here, because 想 is followed by the verb 去 and a destination, it clearly means want to.

They are related, but they are not exactly the same.

In this sentence:

• 想去公园 = want to go to the park
• 要上班 = have to work / need to go to work

A useful way to feel the difference is:

• 想 often expresses a wish, desire, or intention
• 要 often expresses necessity, plan, or something required

So the contrast is very natural:

• 我想去公园，不过我今天要上班。
• I want to go to the park, but I have to work today.

That creates the feeling of:

• desire: 想
• obligation/reality: 要

Mandarin usually puts time expressions early in the sentence, often before the main verb.

So:

• 我今天要上班
• literally: I today need to work

This is normal Chinese word order.

A simple pattern is:

• Subject + Time + Verb Phrase

Examples:

• 我今天上班。 = I work today.
• 他明天去北京。 = He is going to Beijing tomorrow.
• 我们晚上吃饭。 = We eat dinner tonight.

English often places time more flexibly, but Chinese strongly prefers putting it before the main action.

上班 by itself already means to go to work / to be at work / to start work, depending on context.

So:

• 我要上班 can mean I have to go to work
• It does not need 去

Chinese often uses compact verb phrases like this. 上班 is treated as a set expression.

You can also say:

• 我要去上班

This is also correct, but it puts a little more focus on the motion of going. In many everyday situations, 我要上班 is enough.

Yes, often it can be omitted if the subject is clearly the same.

So both of these are natural:

• 我想去公园，不过我今天要上班。
• 我想去公园，不过今天要上班。

The version with the second 我 is a bit fuller and clearer. Repeating the subject is common in Chinese, especially in beginner-style example sentences, because it avoids ambiguity.

So:

• with 我 = explicit, clear, natural
• without 我 = also natural when context is obvious

不过 means but / however.

In this sentence, it introduces a contrast:

• 我想去公园，不过我今天要上班。
• I want to go to the park, but I have to work today.

It is very similar to 但是. In many situations, they are interchangeable.

Compare:

• 我想去公园，不过我今天要上班。
• 我想去公园，但是我今天要上班。

Both are correct.

A rough feeling:

• 不过 can sound a little more conversational or softer
• 但是 can sound a little more direct or formal depending on context

But for learners, both are good words for but.

Mandarin does not have articles like a, an, and the.

So 公园 can mean:

• a park
• the park

The exact meaning depends on context.

In this sentence, 去公园 simply means go to the park or go to a park, depending on what the speaker has in mind. Chinese often leaves that kind of thing unstated unless it really matters.

If you want to make it more specific, Chinese can do that in other ways, for example:

• 去那个公园 = go to that park
• 去一个公园 = go to a park

In Mandarin, 去 + place is the normal pattern for go to + place.

So:

• 去公园 = go to the park
• 去学校 = go to school
• 去北京 = go to Beijing

You usually do not need an extra word for to the way English does. The destination comes directly after 去.

去到 can appear in some contexts, but it is not the basic everyday pattern here. For learners, the safest and most natural structure is:

• 去 + place

The comma is very natural here because the sentence has two parts joined by a contrast word:

• 我想去公园
• 不过我今天要上班

The comma helps show the pause before 不过.

In writing, this is standard and clear:

• 我想去公园，不过我今天要上班。

In casual texting, some people may omit punctuation, but in normal written Chinese the comma is appropriate.

A good way to break it down is:

• 我想去公园
• 不过
• 我今天要上班

Piece by piece:

• 我 = I
• 想 = want to
• 去 = go
• 公园 = park
• 不过 = but / however
• 我 = I
• 今天 = today
• 要 = need to / have to
• 上班 = go to work / work

So the structure is basically:

• Subject + 想 + Verb + Place, 不过 + Subject + Time + 要 + Verb

This is a very useful beginner pattern because it shows both:

• how to express a desire
• how to contrast it with a real-life obligation

Yes, 我想要去公园 is grammatically possible, but 我想去公园 is usually more natural.

Compare:

• 我想去公园 = I want to go to the park
• 我想要去公园 = I want to go to the park

The second one can sound a bit heavier or more emphatic. In many everyday situations, Chinese prefers the simpler form 想 + verb.

So for learners, a very useful pattern is:

• 我想吃饭 = I want to eat
• 我想睡觉 = I want to sleep
• 我想去公园 = I want to go to the park

It can suggest more than one of those in English, depending on context.

要 is a flexible word. Here, 我今天要上班 most naturally means:

• I have to work today
• I need to go to work today

But in other sentences, 要 can also indicate future intention:

• 我要去北京。 = I’m going to Beijing / I want to go to Beijing

So learners should not try to match 要 to only one English word. In this sentence, because it contrasts with 想去公园, the meaning is clearly one of obligation or necessity: I have to work today.