ينتظر الزبون الغاضب هنا.

Because Arabic very commonly uses verb–subject word order, especially in simple statements.

So ينتظر الزبون الغاضب هنا is a very natural Arabic structure:

• ينتظر = waits / is waiting
• الزبون الغاضب = the angry customer
• هنا = here

Arabic can also say:

• الزبون الغاضب ينتظر هنا

That version is also correct, but it gives the subject a bit more prominence. The version with the verb first is especially common in Modern Standard Arabic.

ينتظر is the imperfect verb form of انتظر, from the root related to waiting.

Here it means:

• he waits
• he is waiting

In Modern Standard Arabic, the imperfect can express:

• a present action
• a habitual action
• sometimes a near-future idea, depending on context

So without extra context, ينتظر can be understood as waits or is waiting.

Because the verb itself already contains that information.

ينتظر tells you that the subject is:

• third person
• masculine
• singular

So Arabic does not need a separate pronoun like هو unless you want emphasis or contrast.

Compare:

• ينتظر = he waits / is waiting
• هو ينتظر = he is waiting (with extra emphasis on he)

الزبون has الـ, the Arabic definite article, so it means the customer, not a customer.

In Arabic:

• زبون = a customer
• الزبون = the customer

Since the sentence uses الزبون, it refers to a specific or identifiable customer.

In Arabic, adjectives normally come after the noun they describe.

So:

• الزبون الغاضب = the angry customer

This is the normal pattern:

• noun first
• adjective second

Unlike English, you do not usually put the adjective before the noun.

Because Arabic adjectives agree with the noun in definiteness.

Since the noun is definite:

• الزبون = the customer

the adjective must also be definite:

• الغاضب = the angry

So:

• الزبون الغاضب = the angry customer

If the noun were indefinite, the adjective would also be indefinite:

• زبون غاضب = an angry customer

This matching is very important in Arabic.

The adjective agrees with the noun in several ways:

• definiteness
• gender
• number
• case (in fully vowelled Arabic)

Here:

• الزبون is masculine singular
• الغاضب is also masculine singular

So the agreement is correct.

In full case endings, you would typically have:

• يَنتَظِرُ الزَّبونُ الغاضبُ هنا

Both الزبونُ and الغاضبُ are nominative here.

It functions here like an adjective, but morphologically it is also an active participle.

It comes from the verb غضب = to be angry / become angry.

So غاضب literally has the pattern of someone who is angry. In actual usage, it works very much like an adjective:

• زبون غاضب = an angry customer

Arabic often uses active participles this way.

هنا means here, and it functions as an adverb of place.

It tells you where the waiting is happening.

So:

• ينتظر الزبون الغاضب هنا = The angry customer is waiting here

No preposition is needed before هنا in this sentence.

Yes, Arabic word order is somewhat flexible.

For example, you may also see:

• هنا ينتظر الزبون الغاضب
• الزبون الغاضب ينتظر هنا

All of these are grammatical, though the emphasis may change slightly.

The original order is simple and natural:

• verb
• subject
• place adverb

A fully vowelled version would usually be:

يَنتَظِرُ الزَّبونُ الغاضبُ هنا

Those endings show the grammar more clearly:

• يَنتَظِرُ = imperfect verb
• الزَّبونُ = nominative subject
• الغاضبُ = nominative adjective agreeing with the subject

In normal everyday printed Arabic, these short vowels are often omitted, so you usually see:

• ينتظر الزبون الغاضب هنا

Possibly, but only in the right context.

The imperfect verb in Arabic can sometimes refer to the future, but usually the future is made clearer with words like:

• سـ
• سوف

For example:

• سينتظر الزبون الغاضب هنا = The angry customer will wait here

Without a future marker, the most natural reading is usually present:

• The angry customer waits here
• The angry customer is waiting here