قست المدخل قبل ما نحمل الكنباية، لانه الباب ضيق.

قست means I measured. It is the first-person singular past form of the verb قاس / يقيس to measure.

So in this sentence, the speaker is saying that they measured the entrance before the next action happened.

A common rough pronunciation would be qist or 'ist, depending on the speaker.

In Levantine, the letter ق can sound different by region:

• q in some accents
• a glottal stop in many urban accents
• sometimes g in some regional varieties

So قست المدخل might be heard as something like:

• qist il-madkhal
• 'ist il-madkhal

The exact pronunciation depends on where the speaker is from.

المدخل means the entrance, entryway, or entrance area.

It is not exactly the same as الباب the door.
A door is the physical door itself, while المدخل can mean the whole space/opening you enter through.

That makes sense here: someone may measure the entrance area/opening because the door is narrow.

قبل ما is a very common Levantine way to say before.

So:

• قبل ما نحمل الكنباية = before we carry / before we carried the sofa

In spoken Levantine, قبل ما + imperfect verb is the normal everyday pattern.

Because in Levantine, after قبل ما, speakers usually use the imperfect form, even when the whole sentence is talking about the past.

So:

• قست ... قبل ما نحمل ...
  literally looks like I measured ... before we carry ...

But in natural English, it is often translated as:

• I measured ... before we carried ...

This is normal dialect grammar, not a mistake.

The نـ at the beginning marks first person plural in the imperfect, so:

• نحمل = we carry / we lift

So the subject changes in the sentence:

• قست = I measured
• نحمل = we carry

That means the speaker is talking about an action they did alone first, and then a later action done by a group.

الكنباية means the sofa or the couch.

It is a common colloquial word in Levantine. You may also hear related forms such as كنبة.

A few useful points:

• الـ makes it definite: the sofa
• it is usually treated as a feminine noun
• it is a casual, everyday word, not a very formal one

لانه means because.

In more careful spelling, you may also see:

• لأنه
• لأنو
• لانو

All of these are common ways of writing the same everyday Levantine word. In informal Arabic writing, spelling often varies because people write dialect the way they speak it.

In Arabic, the present-tense verb to be is usually not said.

So:

• الباب ضيق
  literally: the door narrow

but it means:

• the door is narrow

This is completely normal in both spoken Arabic and Standard Arabic when talking about the present.

Because ضيق is describing الباب, and باب is masculine singular.

Arabic adjectives agree with the noun they describe, so:

• الباب ضيق = the door is narrow
• if the noun were feminine, you would use ضيقة

For example:

• البوابة ضيقة = the gate is narrow

In Levantine speech, ضيق is often pronounced something like dayyeʔ.

Yes, it sounds clearly colloquial Levantine, especially because of:

• قبل ما
• الكنباية
• the informal spelling لانه

A more formal version could be:

قِستُ المدخل قبل أن نحمل الأريكة، لأن الباب ضيّق.

Some differences:

• قبل أن is more formal than قبل ما
• الأريكة is a formal word for sofa
• قِستُ includes the formal ending used in Standard Arabic

So the original sentence is very natural for everyday spoken Levantine, while the formal version sounds more like written or news-style Arabic.