النزيل اشتكى من التكييف.

It sounds fairly formal and leans toward Modern Standard Arabic (MSA), even though a Levantine speaker would understand it easily.

The biggest clue is النزيل. In everyday Levantine, people are more likely to say something like:

• الضيف = the guest
• الزبون = the customer
• in a hotel context, sometimes still النزيل, but it sounds more official or hotel-industry-like

Also, in casual Levantine speech, people may phrase the whole sentence a bit differently. For example:

• الضيف اشتكى من التكييف
• الزبون اشتكى من المكيّف
• النزيل اشتكى من التكييف still works, but sounds more formal/report-like

So: correct and understandable, but a bit more formal than everyday street Levantine.

النزيل means the guest, the lodger, or the occupant, especially in a place like a hotel.

In hospitality contexts, it often means:

• hotel guest
• resident guest
• occupant

For an English speaker, the closest idea here is probably the guest.

A useful note: this is not the most common everyday word in casual conversation, but it is common in:

• hotel language
• customer service
• formal reports
• official writing

Because the verb اشتكى normally takes the preposition من when you mean to complain about something.

So:

• اشتكى من التكييف = he complained about the air conditioning

This is the standard pattern:

• اشتكى من الخدمة = he complained about the service
• اشتكت من الصوت = she complained about the noise
• اشتكوا من التأخير = they complained about the delay

So you should learn it as a chunk:

• اشتكى من... = complained about...

Yes. That is a very important point.

اشتكى من can mean:

1. complained about
2. suffered from

The exact meaning depends on context.

Examples:

• اشتكى من التكييف = he complained about the air conditioning
• اشتكى من وجع بالمعدة = he suffered from stomach pain
• اشتكت من الصداع = she suffered from a headache / complained of a headache

So in your sentence, because التكييف is an object of complaint, the meaning is clearly complained about.

اشتكى is the past tense: he complained.

More specifically:

• اشتكى = he complained
• it is third person singular masculine

Some related forms:

• اشتكيت = I complained
• اشتكيتِ = you (feminine singular) complained
• اشتكيتَ = you (masculine singular) complained
• اشتكت = she complained
• اشتكوا = they complained

So in your sentence:

• النزيل اشتكى = the guest complained

Because النزيل is grammatically masculine singular.

Arabic verbs in the past tense agree with the subject in gender and number. So:

• النزيل اشتكى = the male guest complained
• النزيلة اشتكت = the female guest complained

If you were talking about more than one guest:

• النزلاء اشتكوا = the guests complained

So اشتكى matches النزيل.

Because Arabic allows more than one common word order.

Two important patterns are:

• Verb + Subject
• Subject + Verb

In Levantine, subject-first order is very common, especially in everyday speech:

• النزيل اشتكى من التكييف

This feels natural as:

• The guest complained about the air conditioning

A more formal or narrative-style order could be:

• اشتكى النزيل من التكييف

That is also correct.

Very roughly:

• النزيل اشتكى... = common and natural, especially in spoken-style Arabic
• اشتكى النزيل... = also correct, often a bit more formal or report-like

In careful pronunciation, the spelling is:

• النزيل
• التكييف

But because of the sun letters, the ل of الـ is not really pronounced here.

Why?

• ن in النزيل is a sun letter
• ت in التكييف is a sun letter

So they are pronounced approximately like:

• en-naziil / in-naziil
• et-takyiif / it-takyiif

And the whole sentence might sound like:

• en-naziil eshtaka min et-takyiif

Depending on the Levantine variety, vowels may shift a bit, but that gives you the general idea.

اشتكى comes from the root ش ك و / ش ك ي, which has to do with complaint.

A related noun is:

• شكوى = complaint

So you can connect them like this:

• اشتكى = he complained
• شكوى = a complaint

That connection is useful for vocabulary building.

Here التكييف means the air conditioning or the AC system.

This is slightly different from another common word:

• المكيّف = the air conditioner unit / the AC device
• التكييف = air conditioning in general, the cooling system, or the AC

So:

• اشتكى من التكييف = he complained about the air conditioning
• اشتكى من المكيّف = he complained about the air conditioner

In many real-life contexts, either could work depending on what exactly the speaker means.

Yes, من التكييف is understandable and correct. But in everyday Levantine, you may also hear other phrasing.

Possible alternatives include:

• اشتكى من التكييف
• اشتكى من المكيّف
• sometimes colloquially: اشتكى عالتكييف

The version with من is safer for learners because it matches the standard pattern of the verb اشتكى من.

So if you want a reliable form, use:

• اشتكى من...

Because in Levantine speech, and in most normal spoken Arabic, case endings are usually not pronounced.

In very formal MSA, you might theoretically see something like:

• النزيلُ اشتكى من التكييفِ

But in actual spoken Levantine, you would simply say:

• النزيل اشتكى من التكييف

No final -u, -i, etc.

So the sentence looks simple because it reflects normal speech or pause-form pronunciation.

A few more conversational possibilities are:

• الضيف اشتكى من التكييف
• الزبون اشتكى من التكييف
• الضيف اشتكى من المكيّف

Which one you choose depends on context:

• الضيف = guest
• الزبون = customer/client
• النزيل = lodger/guest, more formal or hotel-specific

So if the context is a hotel report, your original sentence is good.
If the context is casual speech, many speakers would probably choose الضيف or الزبون instead.

Here are the most useful changes:

• النزيل اشتكى من التكييف = the male guest complained about the air conditioning
• النزيلة اشتكت من التكييف = the female guest complained about the air conditioning
• النزلاء اشتكوا من التكييف = the guests complained about the air conditioning

Notice the verb changes:

• اشتكى = he complained
• اشتكت = she complained
• اشتكوا = they complained

This is a good sentence for practicing agreement.