اخي قاعد عالكنباية وعم يسمع الراديو.

Because the ending -ي is the possessive suffix my.

• اخ / أخ = brother
• أخي / اخي = my brother

In everyday writing, people often leave out the hamza and write اخي instead of أخي. Both represent the same word here.

In Arabic, the present tense usually does not use a separate word for is / am / are.

So:

• اخي قاعد literally looks like my brother sitting
• but it means my brother is sitting

This is completely normal in both Levantine and Standard Arabic-style structures.

Here, قاعد means sitting.

So:

• اخي قاعد = my brother is sitting

In some Arabic dialect contexts, forms from قاعد can also help express an ongoing action, but in this sentence it is most naturally the literal meaning: he is physically sitting.

It is masculine singular because أخي is masculine singular. If the subject were feminine, you would expect قاعدة.

عالكنباية is a very common spoken contraction of:

• على = on
• الـ = the

Together, they become:

• على الكنباية
• spoken as عالكنباية

This kind of contraction is extremely common in Levantine Arabic.

So:

• عالكنباية = on the couch/sofa

كنباية means couch / sofa in Levantine.

It is a colloquial word, and you may see slight regional spelling or pronunciation differences. In everyday speech, words for furniture often vary a bit from one country or city to another.

عم is a very common Levantine marker used to show an action is happening right now or is in progress.

So:

• يسمع = he listens / he hears
• عم يسمع = he is listening

That is why the sentence uses عم يسمع الراديو for is listening to the radio.

يسمع is the he form, which matches أخي = my brother.

So the agreement is:

• masculine
• singular
• third person

That gives يسمع = he listens / he is listening
With عم, it becomes عم يسمع = he is listening.

If the subject were my sister, the form would be different:

• أختي عم تسمع = my sister is listening

Borrowed words in Arabic can still take the definite article الـ just like native Arabic words.

So:

• راديو = a radio / radio
• الراديو = the radio

That is completely normal.

Also, because ر is a sun letter, the ل in الـ is not pronounced clearly in speech. So الراديو is pronounced more like ir-rādyo / er-rādyo depending on accent.

A common pronunciation would be something like:

akhii qaʿed ʿal-kanbaaye w ʿam yismaʿ ir-raadyo

A few notes:

• خ in أخي is the throaty kh sound
• ع in عال and عم is the Arabic ʿayn
• الراديو is often pronounced with doubled r because of the sun-letter effect

Exact pronunciation will vary a little by region.

It starts as a nominal sentence, because it begins with a noun:

• أخي = my brother

Then it gives information about him:

• قاعد
• وعم يسمع الراديو

So structurally, it begins like a nominal sentence: My brother ...

This is very common in Arabic when describing someone’s current state or action.

They are doing two different jobs:

• قاعد describes his physical position/state: sitting
• عم يسمع describes an action in progress: listening

So the sentence means:

• he is sitting on the couch
• and he is listening to the radio

Even though both relate to what is happening now, they are not redundant. One is a state/posture, and the other is an ongoing action.

Yes. A more formal or Standard-Arabic-like word would be جالس.

So a more formal version might be:

• أخي جالس على الكنباية ويستمع إلى الراديو

But that sounds more formal and less natural as everyday Levantine speech.
For spoken Levantine, قاعد and عم يسمع are much more natural.