هذا عنوان الشركة الجديد.

Because Arabic usually omits the present-tense copula in simple sentences like this.

So:

• هذا = this
• عنوان الشركة الجديد = the company’s new address

Together, Arabic simply says This the company’s new address, but in natural English we translate that as This is the company’s new address.

If you wanted was or will be, Arabic would use other words, but in the present tense it normally leaves is/am/are unstated.

هذا means this and is the masculine singular demonstrative.

It is used here because the thing being pointed to is عنوان (address/title), and عنوان is a masculine singular noun.

So:

• هذا = this for masculine singular nouns
• هذه = this for feminine singular nouns

Even though الشركة is feminine, the main noun being referred to is عنوان, so هذا is correct.

Because عنوان الشركة is an iḍāfa construction, often called a genitive or possessive phrase.

In an iḍāfa:

• the first noun usually does not take الـ
• the second noun shows who or what the first noun belongs to

So:

• عنوان الشركة = the company’s address / address of the company

Even without الـ on عنوان, the whole phrase can still be definite because الشركة is definite.

It is an iḍāfa phrase:

• عنوان = address
• الشركة = the company

Together:

• عنوان الشركة = the company’s address

This is how Arabic commonly expresses possession or close relationships between nouns.

English often uses:

• the company’s address
• the address of the company

Arabic usually uses the noun-noun structure instead.

Because adjectives in Arabic normally come after the noun they describe.

Here, الجديد means new and describes عنوان الشركة.

So the order is:

• noun phrase first: عنوان الشركة
• adjective after it: الجديد

That gives:

• عنوان الشركة الجديد = the company’s new address

This is normal Arabic word order for nouns and adjectives.

Because the noun phrase it describes is definite.

Even though عنوان itself does not have الـ, the whole iḍāfa phrase عنوان الشركة is definite because الشركة is definite.

Since adjectives must agree with the noun they modify in definiteness, the adjective is also definite:

• عنوان الشركة = definite
• الجديد = therefore also definite

That is why you get الجديد, not جديد.

Because الجديد is describing عنوان, not الشركة.

The head noun of the phrase is عنوان, and عنوان is:

• masculine
• singular

So the adjective must also be:

• masculine
• singular

That gives الجديد.

If the head noun were feminine, the adjective would have to be feminine too.

In fully vocalized formal Arabic, it would be:

• هٰذا عُنْوانُ الشَّرِكَةِ الجَديدُ

Here is the grammar:

• هٰذا = demonstrative, fixed form
• عُنْوانُ = nominative, because it is the predicate of the sentence
• الشَّرِكَةِ = genitive, because it is the second term of the iḍāfa
• الجَديدُ = nominative adjective matching عنوان

In everyday reading and speech, these final short vowels are often not pronounced.

In الشركة, the ل of الـ is not pronounced because ش is a sun letter.

So:

• written: الشركة
• pronounced: ash-sharika (or ash-sharikah in pause)

By contrast, in الجديد, the ل is pronounced because ج is not a sun letter:

• al-jadīd

So the whole sentence is roughly pronounced:

• hādhā ʿunwān ash-sharika al-jadīd

In fully inflected formal reading, you may hear:

• hādhā ʿunwānu ash-sharikati al-jadīdu

Yes. عنوان can mean:

• address
• title
• sometimes heading

The exact meaning depends on context.

So عنوان الشركة الجديد could, in another context, mean:

• the company’s new title
• the company’s new heading/name label

But if the meaning has already been given as address, then that is the intended reading here.

Yes, that is also possible, but the structure is slightly different.

• هذا عنوان الشركة الجديد = This is the company’s new address
• هذا العنوان الجديد للشركة = This is the new address of the company / This new address belongs to the company

The original sentence uses an iḍāfa first: عنوان الشركة.
The alternative puts العنوان الجديد together first, then adds للشركة.

Both can be correct, but the original is a very natural and compact way to express the company’s new address in Arabic.