בקיץ הרחוב הזה תמיד צפוף, כי הרבה אנשים הולכים לים.

In Hebrew, the verb to be is usually not expressed in the present tense.

So:

• הרחוב הזה תמיד צפוף = This street is always crowded

Literally, Hebrew says something like:

• this street always crowded

But it is completely normal and grammatical.
In past or future, Hebrew does use forms of to be:

• הרחוב הזה היה צפוף = This street was crowded
• הרחוב הזה יהיה צפוף = This street will be crowded

In Hebrew, demonstratives like this usually come after the noun:

• הרחוב הזה = this street
• הבית הזה = this house
• האנשים האלה = these people

This is different from English, where this comes before the noun.

Also, the noun is usually definite:

• רחוב = a street
• הרחוב הזה = this street

So the normal pattern is:

• ה + noun + זה/זאת/האלה

בקיץ is made of:

• ב־ = in
• קיץ = summer

So literally it means in summer or in the summer.

Hebrew often attaches prepositions directly to the following word, so instead of writing two separate words, it becomes one:

• ב + קיץ = בקיץ

If the noun is definite, the ה often disappears after certain prepositions:

• ב + ה + קיץ becomes בקיץ

This is very common:

• בבית = in the house / at home
• בשבוע הבא = in the coming week
• לים = to the sea

Because it describes הרחוב (the street), which is a masculine singular noun.

Hebrew adjectives must agree with the noun in:

• gender
• number

So:

• רחוב צפוף = a crowded street
• עיר צפופה = a crowded city
• רחובות צפופים = crowded streets
• ערים צפופות = crowded cities

In this sentence, צפוף is used as a predicate adjective:

• הרחוב הזה תמיד צפוף = This street is always crowded

It still agrees with הרחוב.

תמיד means always, and in this sentence it naturally comes before the adjective:

• הרחוב הזה תמיד צפוף

This is a very normal word order in Hebrew.

You can think of the structure as:

• topic: הרחוב הזה
• time/frequency word: תמיד
• description: צפוף

Hebrew word order is somewhat flexible, but this version sounds very natural.

כי means because.

It introduces the reason:

• הרחוב הזה תמיד צפוף = This street is always crowded
• כי הרבה אנשים הולכים לים = because many people go to the sea/beach

So the whole sentence means:

• This street is always crowded in the summer, because many people go to the beach/sea.

כי is one of the most common ways to say because in everyday Hebrew.

הרבה means many or a lot of.

So:

• הרבה אנשים = many people
• literally: a lot of people

This is a very common everyday way to express quantity in Hebrew.

Another possible, more formal-sounding option is:

• אנשים רבים = many people

But הרבה אנשים is extremely common and natural in speech and writing.

הולכים is the masculine plural present-tense form of הלך (to go / walk).

It matches אנשים (people), which is grammatically masculine plural.

Important point: in Hebrew, the masculine plural is often used for:

• a group of men
• a mixed-gender group
• people in general

So הרבה אנשים הולכים לים does not mean only men are going. It can easily mean many people in a general sense.

Compare:

• הוא הולך = he goes / is going
• היא הולכת = she goes / is going
• הם הולכים = they go / are going
• הן הולכות = they go / are going (all feminine)

It can mean more than one thing, depending on context.

The Hebrew present tense often covers both:

• go
• are going

So:

• הרבה אנשים הולכים לים

can mean:

• many people go to the beach
• many people are going to the beach

In this sentence, because of תמיד and בקיץ, the meaning is clearly habitual:

• many people go to the beach

Also, הלך / הולך can sometimes mean walk, but here הולכים לים is best understood as go to the beach/sea, not necessarily walk to the beach.

לים is made of:

• ל־ = to
• ים = sea

When ל־ is attached to a definite noun with ה, the ה usually gets absorbed:

• ל + הים = לים

So לים means to the sea or to the beach.

This also happens with other prepositions:

• ב + הבית = בבית = in the house
• כ + המלך = כמלך = like the king

So even though you do not see a separate ה, the noun can still be definite.

Literally, לים means to the sea.

But in everyday Hebrew, ללכת לים often means:

• to go to the beach
• to go to the seaside

So in this sentence, the natural English meaning is usually:

• many people go to the beach

Even though the Hebrew word is literally sea, the broader real-life meaning is often beach.

The comma separates the main statement from the reason clause:

• בקיץ הרחוב הזה תמיד צפוף, כי הרבה אנשים הולכים לים.

This is similar to English:

• In the summer, this street is always crowded, because many people go to the beach.

In modern Hebrew punctuation, this comma is normal and helps readability, especially in a sentence with two clauses.

Yes. Hebrew allows some flexibility in word order.

For example, these are all possible:

• בקיץ הרחוב הזה תמיד צפוף, כי הרבה אנשים הולכים לים.
• הרחוב הזה תמיד צפוף בקיץ, כי הרבה אנשים הולכים לים.

Both are natural. The version in your sentence puts בקיץ first, which gives early time context:

• In the summer, ...

That is often a very natural way to begin a sentence in Hebrew.