صاحبي نسي تليفونه في البيت.

A useful pronunciation is:

ṣāḥbi nesi tilifōnu fil-bēt

A more learner-friendly version:

SAH-bi NE-si tili-FO-nu fil-BEIT

A few pronunciation notes:

• ص is a heavy/emphatic s
• ح is a strong breathy h from the throat
• نسي is nesi
• تليفونه ends with a possessed -u/-o sound in speech, even though it is written with ه
• في البيت is often said together as fil-bēt

صاحبي means my friend or my buddy.

It is made of:

• صاحب = friend, companion
• -ي = my

So:

• صاحب = friend
• صاحبي = my friend

In Egyptian Arabic, صاحبي is very common in everyday speech and can sound casual and natural, like my friend / my buddy / a friend of mine, depending on context.

Both can mean my friend, but they feel a little different.

• صاحبي is very common in Egyptian spoken Arabic
• صديقي is more formal or more associated with Modern Standard Arabic

So in everyday Egyptian speech, صاحبي sounds more natural here.

نسي means forgot.

It is a past tense verb, so the sentence is talking about something that already happened.

Here it means:

• نسي = he forgot

Arabic often does not need to state he separately, because the verb already tells you that the subject is he.

Because Arabic verbs often already include the subject.

In نسي, the verb itself already means he forgot.

So Arabic does not need an extra word like هو here.

You could say هو نسي تليفونه, but in a normal sentence that would often be unnecessary unless you want emphasis.

تليفونه means his phone.

It is built like this:

• تليفون = telephone / phone
• -ه = his

So:

• تليفون = phone
• تليفونه = his phone

This is very normal in Arabic. Instead of saying phone of him as separate words, Arabic usually attaches the possessive ending directly to the noun.

In Egyptian pronunciation, -ه in this kind of word is often heard as -u or -o, so تليفونه sounds like tilifōnu.

تليفون is the everyday Egyptian word for phone/telephone.

هاتف is more formal and more typical of Modern Standard Arabic.

So:

• تليفونه = his phone, everyday Egyptian
• هاتفه = his phone, more formal/standard

If you are learning spoken Egyptian, تليفون is the more useful everyday word.

Literally, في البيت means in the house.

But in natural English, it often means at home.

Breakdown:

• في = in / at
• البيت = the house / the home

So depending on context:

• literal: in the house
• natural translation: at home

Because Arabic often uses البيت in the same situations where English would say home.

So in this sentence, في البيت naturally corresponds to at home, even though word-for-word it is in the house.

This is a very common and natural usage.

In Egyptian Arabic, subject + verb + object is very common in everyday speech.

So:

• صاحبي = my friend
• نسي = forgot
• تليفونه = his phone

That gives:

My friend forgot his phone

Starting with the subject is extremely normal in spoken Egyptian.

Yes, in real-life context it might be understood that way.

The literal meaning of نسي تليفونه is forgot his phone. But in English, when someone forgets their phone somewhere, we often naturally say left his phone at home.

So:

• literal: My friend forgot his phone at home
• natural English in many situations: My friend left his phone at home

The Arabic verb here is still forgot, not a separate verb meaning left behind.

It is best understood as Egyptian Arabic or at least colloquial Arabic with Egyptian flavor.

Why?

• صاحبي is very common in spoken Egyptian
• تليفون is a common colloquial word
• the overall sentence sounds natural in everyday speech

A more formal Modern Standard Arabic version might be something like:

صديقي نسي هاتفه في البيت

But the sentence you have is the kind of Arabic you are likely to hear in daily Egyptian conversation.

Yes, especially these:

• ص in صاحبي: a heavy/emphatic s
• ح in صاحبي: a throatier h than English h
• بيت in البيت: the vowel often sounds like bēt
• the attached pronoun in تليفونه: written -ه, but often pronounced more like -u/-o

If you say the whole sentence smoothly, try:

ṣāḥbi nesi tilifōnu fil-bēt

That will sound much closer to natural Egyptian speech.