بعد دقيقة، الميه هتغلي.

Here it means in a minute / after one minute has passed.

So بعد دقيقة، الميه هتغلي means the boiling will happen one minute from now. In English, after a minute and in a minute can both fit this idea, but in a minute is often the most natural translation here.

Because Egyptian Arabic often shows the future by adding هـ to the present-tense verb.

• تغلي = it boils / it is boiling
• هتغلي = it will boil

So the هـ at the beginning of هتغلي is doing the job of English will.

Because الميه is commonly treated as feminine in Egyptian Arabic, so the verb takes the 3rd person feminine singular form.

That gives:

• هيغلي = he/it (masculine) will boil
• هتغلي = she/it (feminine) will boil

Since الميه is feminine in this usage, هتغلي is the expected form.

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

Compare:

• Egyptian Arabic: الميه
• Modern Standard Arabic: الماء

So if you are learning Egyptian, الميه is the everyday word you will hear most often.

A natural pronunciation is:

baʿd daʔīʔa, el-mayya hatighli

A few notes:

• بعد = baʿd
• دقيقة is pronounced with a glottal stop in Egyptian: daʔīʔa
• الميه is often said as el-mayya
• غ in هتغلي is the Arabic gh sound, like a voiced throaty/fricative sound

Yes, absolutely.

Both are natural:

• بعد دقيقة، الميه هتغلي.
• الميه هتغلي بعد دقيقة.

Putting بعد دقيقة first gives a little more emphasis to the time: In a minute, the water will boil.

Putting it at the end sounds more like a neutral statement: The water will boil in a minute.

You do not need واحدة here.

In Arabic, a singular noun by itself can often mean one of that thing when the meaning is clear:

• دقيقة = a minute / one minute

You could say بعد دقيقة واحدة for extra emphasis, but it is less necessary in everyday speech. بعد دقيقة is the normal, natural way.

Without هـ, تغلي is the present/imperfect form. Depending on context, it could mean things like:

• it boils
• it is boiling

With هـ, it becomes future:

• هتغلي = it will boil

So the هـ is the key thing shifting the meaning forward in time.

Yes, by itself it could.

Arabic verb forms can be ambiguous out of context, and هتغلي could theoretically mean:

• she/it will boil
• you (feminine singular) will boil

But in this sentence, the subject الميه comes right before the verb, so the meaning is clearly:

the water will boil

It is specifically Egyptian Arabic because of forms like:

• الميه instead of الماء
• the future marker هـ

A Modern Standard Arabic version would be something like:

• بعد دقيقة، سيغلي الماء.

So the sentence you have is natural for spoken Egyptian, not formal written Standard Arabic.

Because the sentence is talking about a specific water that both speakers understand from context, for example water in a pot or kettle.

So:

• الميه = the water

If you removed الـ and said ميه, that would sound more like water in a more general or indefinite sense. In this sentence, the water is the natural choice.