jīntiān gōngyuán lǐ yǒu hěn duō rén, hěn yōngjǐ.

In Chinese, time words often come near the beginning of the sentence, before the main description.

So:

• 今天公园里有很多人 = Today, in the park, there are many people

This is very natural in Mandarin. A common word order is:

Time + Place + 有 + Thing/Person

For example:

• 今天家里有客人。 = There are guests at home today.

You could move 今天 in some contexts, but putting it first is one of the most common and natural choices.

Both can work, but 公园里有很多人 is very natural.

• 公园里 = in the park
• 在公园里 = at/in the park

When Chinese uses the 有 pattern to say that something exists somewhere, the place can often come directly before 有 without 在:

• 公园里有很多人。
• 桌子上有一本书。
• 房间里有猫。

Adding 在 is possible in some cases, but with existence sentences, it is often omitted because the location already functions clearly on its own.

里 means inside or in.

So:

• 公园 = park
• 公园里 = in the park

It is a location word. You will often see it after a place noun:

• 家里 = at home / in the house
• 教室里 = in the classroom
• 包里 = in the bag

In this sentence, 公园里 tells us the location where the people are.

Here, 有 means there is / there are.

So:

• 公园里有很多人 literally = In the park there are many people

This is a very common Chinese pattern for saying something exists somewhere:

Place + 有 + noun

Examples:

• 桌子上有一杯咖啡。 = There is a cup of coffee on the table.
• 学校里有很多学生。 = There are many students in the school.

So 有 here is not really have in the English possessive sense. It is an existence pattern.

Because 人 already means people, and that is the normal word to use here.

• 很多人 = many people

人们 also means people, but it is used differently. It is more general, often talking about people as a group in a broader or more abstract sense. It is not usually used after numbers or quantity words like 很多 in this kind of sentence.

So:

• 公园里有很多人。 = natural
• 公园里有很多人们。 = unnatural

Think of 人们 more like people in general:

• 人们都很关心这个问题。 = People all care about this issue.

Because 很多 can directly modify some nouns, including 人.

So:

• 很多人 = many people
• 很多书 = many books
• 很多地方 = many places

You do not need a measure word here.

By contrast, if you use a specific number, you usually do need one:

• 三个人 = three people
• 五本书 = five books

So 很多 behaves differently from exact numbers.

This is a very common point for English speakers.

In Chinese, adjectives often need an adverb like 很 when they act as the main predicate of a sentence.

So:

• 很拥挤 = very crowded
• but sometimes 很 does not feel as strong as English very

In beginner Chinese, you often learn that:

• 他很高。 literally = He very tall but in actual usage it often just means He is tall

In this sentence, though, 很 can still carry some real emphasis, so 很拥挤 naturally means very crowded.

Without 很, 拥挤 can sound more abrupt or contrastive depending on context.

The subject is understood from context.

The sentence is:

• 今天公园里有很多人，很拥挤。

After saying there are many people in the park, the next part 很拥挤 describes the overall situation: the park, the area, or the scene feels crowded.

Chinese often leaves the subject unstated when it is obvious.

In more explicit Chinese, you could say:

• 今天公园里有很多人，公园很拥挤。 = There are many people in the park today, and the park is very crowded.

But repeating 公园 is unnecessary here, so native speakers often omit it.

拥挤 means crowded, packed, or congested. It is slightly more formal and descriptive than 挤.

• 拥挤 often describes a place, traffic, or a situation with too many people or things in one space.
• 挤 can also mean crowded, but it can additionally mean to squeeze, to press, or to push into a tight space.

Examples:

• 地铁很拥挤。 = The subway is very crowded.
• 车上很挤。 = It’s crowded on the bus.
• 别挤！ = Don’t push!

So in your sentence, 拥挤 is a good word because it describes the park’s crowded condition clearly.

Chinese often links related ideas with just a comma, especially when the relationship is easy to understand from context.

Here:

• 今天公园里有很多人，很拥挤。

The logic is:

• There are many people in the park today
• so it is crowded

Chinese does not always need to state the connection explicitly. The comma is enough.

If you wanted, you could make the connection more explicit:

• 今天公园里有很多人，所以很拥挤。 = There are many people in the park today, so it’s very crowded.

But the original version is more natural and concise.

Yes, depending on context, that is a very natural English translation.

The Chinese sentence literally gives two ideas:

• There are many people in the park today
• It is very crowded

Natural English often combines them into:

• The park is crowded today.
• The park is very crowded today.
• There are a lot of people in the park today, so it’s crowded.

So even though the Chinese structure uses 有, the best English translation may be more flexible than a word-for-word version.