nàge nánháizi zài gōngyuán lǐ dǎlánqiú.

个 is a measure word/classifier. In Mandarin, when you use 这 or 那 before most nouns, you usually need a classifier in between.

The pattern is:

这 / 那 + measure word + noun

So:

• 那个男孩子 = that boy
• literally: that + classifier + boy

For people and many everyday nouns, 个 is the most common general classifier.

In standard Mandarin, that usually sounds incomplete or unnatural.

You normally say:

• 那个男孩子

not:

• 那男孩子

So for learners, it is best to remember that 这/那 usually need a classifier before the noun.

It is usually pronounced nàge in normal speech, with 个 often becoming a neutral tone.

So although the dictionary tone for 个 is fourth tone, in this phrase learners will often hear:

• nàge

rather than a very strong:

• nàgè

This is very common in natural spoken Mandarin.

Both mean boy.

• 男孩 is shorter and very common.
• 男孩子 is also common, and can sound a little more conversational or child-focused.

In many situations, they are interchangeable. So this sentence could also be:

• 那个男孩在公园里打篮球。

with basically the same meaning.

This is a common way to express location in Mandarin:

在 + place + 里

So:

• 在 = at / in
• 公园 = park
• 里 = inside

Together, 在公园里 means in the park.

This is a very common structure for saying where something happens.

Not always. You can often say either:

• 在公园里打篮球
• 在公园打篮球

Both are natural.

Adding 里 makes the sense of inside the park / in the park a little more explicit. With a place like 公园, 里 is often optional.

Chinese usually puts time and place information before the main verb.

So the sentence order is:

subject + location + verb phrase

Here:

• 那个男孩子 = subject
• 在公园里 = location
• 打篮球 = main action

In English, we often put the location later:

• That boy is playing basketball in the park.

But in Mandarin, putting the location before the verb is very normal.

By itself, 打 can mean things like hit, strike, or play depending on context.

With many sports involving a ball, Mandarin uses 打 as the normal verb:

• 打篮球 = play basketball
• 打网球 = play tennis
• 打乒乓球 = play table tennis

So in this sentence, 打篮球 is just the standard way to say play basketball.

Grammatically, it is a verb-object phrase:

• 打 = play
• 篮球 = basketball

So it is literally play basketball.

Even though it is made of two parts, learners often memorize 打篮球 as a set expression because it functions like one action in everyday speech.

No. In this sentence, 在 is a preposition showing location, meaning at/in.

So:

• 在公园里 = in the park

It is not the same as the 在 sometimes used before a verb to show an ongoing action.

For example:

• 那个男孩子在打篮球。
• 那个男孩子正在打篮球。

Both can mean That boy is playing basketball.

So in your sentence, the first 在 is about where, not about ongoing aspect.

Mandarin does not mark tense the way English does, so the exact time meaning often depends on context.

This sentence can be understood as:

• That boy is playing basketball in the park
• or, in some contexts, That boy plays basketball in the park

If this is describing a picture or something happening right now, people will usually understand it as is playing basketball.

If you want to make the ongoing action clearer, you can say:

• 那个男孩子正在公园里打篮球。

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

Instead, specificity is shown in other ways. Here, 那个 already makes the noun specific:

• 那个男孩子 = that boy

If you removed 那个, then 男孩子 could mean a boy, the boy, or just boy depending on context.

So Mandarin relies much more on context and words like 这 and 那 than on articles.