المكان ده هادي بالليل.

A natural Egyptian pronunciation is:

il-makān da hādi bil-lēl

A rough word-by-word guide:

• المكان → il-makān
• ده → da or sometimes deh in transliteration
• هادي → hādi
• بالليل → bil-lēl

You may hear small differences depending on the speaker, but this is a very normal everyday pronunciation.

Because Egyptian Arabic often uses a nominal sentence in the present tense. That means there is no separate present-tense verb to be.

So the structure is:

• المكان ده = the subject, this place
• هادي = the description/predicate, quiet / calm
• بالليل = time phrase, at night

So Arabic simply says something like:

this place quiet at night

and the meaning is is understood automatically.

ده is the Egyptian Arabic masculine singular demonstrative, meaning this.

In Egyptian Arabic, demonstratives usually come after the noun:

• المكان ده = this place
• literally: the place this

This is different from English, and also different from the most common MSA pattern, where the demonstrative usually comes first:

• هذا المكان

So المكان ده is a very normal Egyptian way to say this place.

Yes. المكان is masculine singular, so ده is the correct form.

With a feminine singular noun, Egyptian Arabic usually uses دي instead.

For example:

• المنطقة دي هادية بالليل = this area is quiet at night

You also see agreement in the adjective:

• masculine: هادي
• feminine: هادية

So both the demonstrative and the adjective can reflect the gender of the noun.

Because المكان is masculine singular, so the adjective is masculine singular too:

• مكان هادي
• منطقة هادية

If the noun were feminine, you would usually add ـة / -a at the end of the adjective:

• المنطقة دي هادية

So هادي matches المكان correctly.

هادي is the normal Egyptian colloquial form.
هادئ is the Modern Standard Arabic form.

This is a very common pattern: colloquial Egyptian often simplifies words that are more formal in MSA.

So:

• Egyptian: هادي
• MSA: هادئ

If you are learning spoken Egyptian, هادي is the form you want here.

بالليل is the usual Egyptian way to say at night.

It is made from:

• بـ = a preposition, often like in / at / by
• الليل = the night

So literally it is something like in the night or at the night, but the natural English meaning is just at night.

In everyday Egyptian, بالليل is much more natural than a more formal expression like في الليل.

For two different reasons:

1. المكان
The noun is definite because المكان ده means this place, not just a place. In Egyptian Arabic, a noun with ده is normally definite:

• المكان ده = this place

2. الليل
In the time expression بالليل, the noun ليل commonly appears with the article, giving the fixed everyday phrase بالليل = at night.

So both are completely normal here.

A natural MSA version would be:

هذا المكان هادئ في الليل

or sometimes:

هذا المكان هادئ ليلًا

The main differences are:

• Egyptian: المكان ده
• MSA: هذا المكان

and

• Egyptian: هادي
• MSA: هادئ

So the sentence you were given is clearly colloquial Egyptian, not formal MSA.

You can negate it with مش:

المكان ده مش هادي بالليل

That means this place is not quiet at night.

In Egyptian Arabic, مش is the normal way to negate this kind of present-tense nominal sentence.