الميه بتغلي في الغلاية.

It is Egyptian Arabic.

Two big clues are:

• الميه = Egyptian for water
• بتغلي = Egyptian present-tense form

In Modern Standard Arabic, you would more likely see:

• الماء يغلي في الغلاية

So this sentence is clearly colloquial Egyptian, not formal written Arabic.

A natural pronunciation is:

el-mayya bitighli fil-ghallāya

You may also hear il- instead of el-, depending on the speaker.

Rough breakdown:

• الميه → el-mayya
• بتغلي → bitighli
• في الغلاية → fil-ghallāya

Notice that في الغلاية often runs together in speech, so fi el- becomes fil-.

Yes. الميه means the water, and it is the everyday Egyptian Arabic word for water.

Compare:

• الميه = Egyptian colloquial
• الماء = Modern Standard Arabic / formal Arabic

You will also often see المية spelled with ية instead of يه. Both spellings are common in informal Egyptian writing.

In Egyptian Arabic, the prefix بـ is very common in the present tense.

So:

• تغلي → boil
• بتغلي → boils / is boiling

This بـ often marks the normal present or ongoing action in Egyptian speech.

That means بتغلي can mean:

• boils
• is boiling

The exact English translation depends on context.

Because الميه is treated as feminine in Egyptian Arabic.

So the verb agrees with it:

• هي بتغلي = she/it is boiling
• الميه بتغلي = the water is boiling

If the subject were masculine singular, you would normally get بيغلي instead.

This is something English speakers often need to get used to: even objects and substances can be grammatically masculine or feminine.

It can mean either one.

In Egyptian Arabic, the present form often covers both:

• a general truth or regular action: boils
• something happening now: is boiling

So this sentence could mean:

• The water boils in the kettle
• The water is boiling in the kettle

In most everyday situations, people would probably understand it as is boiling, unless the context suggests a general statement.

في means in or inside.

So:

• في الغلاية = in the kettle

Very often in speech:

• في الغلاية is pronounced fil-ghallāya

That happens because في and الـ get connected smoothly in pronunciation.

Yes, you could say both, but they mean slightly different things.

• في الغلاية = in the kettle
  a specific kettle, known from context

• في غلاية = in a kettle
  any kettle, not a specific one

So in your sentence, الغلاية is definite because the speaker means a particular kettle.

Yes, the ل stays.

A natural pronunciation is:

el-ghallāya

That is because غ is a moon letter, not a sun letter. With moon letters, the ل of الـ is pronounced.

So:

• الغلاية → el-ghallāya

Compare that with sun-letter words, where the ل disappears in pronunciation.

Yes, they are related.

Both come from the idea of boiling:

• بتغلي = is boiling / boils
• غلاية = kettle, boiler

So this is a nice vocabulary pair to remember:

• غلي / يغلي = to boil
• غلاية = something used for boiling, especially a kettle

Yes, but the original order is the most neutral and natural:

• الميه بتغلي في الغلاية

This is a very normal Egyptian pattern: subject + verb + place.

You might hear other orders for emphasis, such as putting the place first, but the sentence you have is the best basic version for a learner.

For example:

• في الغلاية، الميه بتغلي
  = emphasizes in the kettle

But if you are just learning the structure, stick with:

• الميه بتغلي في الغلاية