سالت الكاشير: فيه فستان بالمقاس ده؟

A natural Egyptian-style pronunciation would be roughly:

sa'alt el-kashīr: fīh fostān bel-meʔās da?

A few pronunciation notes:

• سالت / سألت = sa'alt
  There is usually a little break between the vowels because of the hamza.
• الكاشير = el-kashīr
• فيه = fīh
• فستان = fostān or fustān
• مقاس in Egyptian is often pronounced meʔās, because ق often becomes a glottal stop.
• ده = da

Because Arabic verbs usually already include the subject.

So سألت / سالت by itself means I asked.

You can add أنا if you want emphasis:

أنا سألت الكاشير

But in normal speech, that is usually unnecessary.

In careful spelling, especially in Standard Arabic, it would normally be written سألت.

In casual Egyptian writing, people often leave out the hamza and write سالت instead. That does not usually mean the pronunciation changes to saalet. It still usually means sa'alt in context.

So:

• سألت = careful / standard spelling
• سالت = very common casual spelling in dialect writing

Here فيه means there is / there are.

So فيه فستان...؟ means Is there a dress...?

This is a very common Egyptian way to ask about availability. It is much more natural in everyday speech than a formal expression like هل يوجد.

Also, this فيه is different from في meaning in.

• في البيت = in the house
• فيه فستان؟ = is there a dress?

Because the speaker is asking whether any dress in that size is available, not asking about one specific dress.

So:

• فيه فستان بالمقاس ده؟ = Is there a dress in this size?
• فيه الفستان بالمقاس ده؟ would sound like you mean the dress, a specific one already known in the conversation.

After فيه, an indefinite noun is very common when asking whether something exists or is available.

Literally, it is something like with this size or in this size.

Breakdown:

• بـ = with / in / by
• المقاس = the size
• ده = this

So بالمقاس ده means in this size.

In shopping Arabic, this is a very natural way to talk about size.

In Egyptian Arabic, بـ is often used in expressions where English uses in.

So:

• بالمقاس ده = in this size
• باللون ده = in this color
• بالشكل ده = like this / in this form

It is just the natural preposition used in this kind of shopping expression.

Because in Egyptian Arabic, demonstratives like ده and دي usually come after the noun.

So:

• الكتاب ده = this book
• البنت دي = this girl
• المقاس ده = this size

This is one of the big differences from English.

Also notice that the noun is usually definite in this structure:

• المقاس ده not usually
• مقاس ده

It refers to المقاس.

So the phrase means:

in this size

not

this dress

If you wanted to say this dress, you would say:

الفستان ده

But here the structure is:

فستان + بالمقاس ده

So the focus is on the size, not on a specific dress.

الكاشير is a very common everyday loanword meaning cashier.

In shops and malls, Egyptians often use this borrowed word naturally in conversation. It behaves like a normal Arabic noun, so it can take ال:

• كاشير = cashier
• الكاشير = the cashier

A more formal Arabic equivalent exists, but in everyday Egyptian speech الكاشير sounds much more natural.

Usually, this sentence can stay the same.

سألت الكاشير simply means I asked the cashier, and الكاشير is often used for either a male or female cashier in colloquial speech.

Some speakers may say الكاشيرة for a female cashier, but الكاشير is very common either way.

So in everyday speech, you usually do not need to change anything.

Yes, this is natural.

But there are a few other very common ways to ask the same thing in Egyptian:

• فيه فستان بالمقاس ده؟ = Is there a dress in this size?
• عندكم فستان بالمقاس ده؟ = Do you have a dress in this size?
• عندكوا فستان بالمقاس ده؟ = same idea, very common when speaking to store staff
• ممكن ألاقي فستان بالمقاس ده؟ = Could I find a dress in this size?

All of these sound normal in a shopping context.

The colon is just showing that what comes next is the exact question the speaker asked.

So the structure is:

• سالت الكاشير: = I asked the cashier:
• فيه فستان بالمقاس ده؟ = Is there a dress in this size?

It works like direct speech in English. In casual writing, people may use punctuation loosely, or sometimes not at all.