هو بيستنى اختي عند باب العمارة.

A common Egyptian pronunciation is:

howwa biyestanna okhti ʿand bāb el-ʿamāra

A few helpful sound notes:

• خ in اختي / أختي is like the ch in German Bach or Scottish loch
• ع in عند and العمارة is the Arabic ʿayn, a throat sound with no exact English equivalent
• العمارة here is usually pronounced el-ʿamāra in Egyptian

You may also see slightly different transliterations, like huwwa, biyistanna, or ukhti.

Not strictly.

Arabic verbs already show the subject, so بيستنى by itself can mean he waits / he is waiting from context. That means:

• هو بيستنى اختي عند باب العمارة
• بيستنى اختي عند باب العمارة

can both work.

Including هو can make the sentence feel clearer, more explicit, or slightly more emphatic: he is waiting.

بيستنى is the Egyptian present-tense form of the verb استنى, which means to wait.

The prefix بـ in Egyptian Arabic is very common in the present tense. It often corresponds to English waits, is waiting, or does wait, depending on context.

So:

• استنى = he waited / wait!
• يستنى = he wait(s) in certain grammatical environments
• بيستنى = he waits / he is waiting

This is a very Egyptian-style everyday verb. In Modern Standard Arabic, a learner might expect ينتظر, but in Egyptian يستنى / بيستنى is much more common in speech.

Because in Egyptian Arabic, استنى can take a direct object.

So:

• بيستنى اختي = he is waiting for my sister

English needs wait for someone, but Arabic does not have to use a separate word equivalent to for here.

This is a very common difference from English.

Yes, the more careful spelling is أختي.

In casual Arabic writing, especially in dialect, people often drop the initial hamza/alif and write اختي instead. So:

• أختي = more standard spelling
• اختي = very common casual spelling

Both are understood as my sister.

Also, the ending ـي means my, so:

• أخت = sister
• أختي = my sister

And because it has a possessive ending, it is already definite, so you do not add ال.

Because the word is based on أخت.

When a noun like this takes a suffix, the final t is pronounced clearly:

• أخت = sister
• أختي = my sister

So it is pronounced roughly okhti / ukhti, not something like okhii.

Here, عند means at, by, or near.

So عند باب العمارة means something like:

• at the building entrance
• by the building door

This is more natural here than في, because في usually means in / inside. If someone is waiting outside or right by the entrance, عند fits better.

Because this is an iḍāfa construction, which is how Arabic expresses possession or X of Y.

So:

• باب العمارة = the door of the building / the building entrance

In an iḍāfa:

• the first noun usually does not take ال
• the second noun can be definite
• the whole phrase becomes definite if the second noun is definite

That is why باب العمارة is correct, not الباب العمارة.

In Egyptian Arabic, عمارة usually means an apartment building or residential building.

So باب العمارة often means the main entrance of the apartment building, not just any random door.

A very natural English rendering would often be at the entrance to the building.

It can mean either one, depending on context.

In Egyptian Arabic, the present form with بـ can cover both:

• he waits
• he is waiting

If this sentence appears in a scene happening now, most people will understand it as he is waiting. If it is describing a habit, it can mean he waits.

Context decides.

Yes, absolutely. That is very natural in Egyptian Arabic.

مستني is also commonly used for waiting. In many everyday situations:

• هو بيستنى اختي عند باب العمارة
• هو مستني اختي عند باب العمارة

both sound fine.

Very roughly:

• بيستنى = present-tense verb form
• مستني = active participle, often used for a current state

In real conversation, مستني can sound especially natural for he is waiting right now.