احنا هنروح حفلة عيد ميلاد صاحبي يوم السبت.

احنا means we in Egyptian Arabic. You will also often see it written as إحنا.

It is not strictly necessary in this sentence, because the verb already shows that the subject is we. So both of these are natural:

• احنا هنروح حفلة عيد ميلاد صاحبي يوم السبت
• هنروح حفلة عيد ميلاد صاحبي يوم السبت

Including احنا can make the sentence clearer, more conversational, or slightly more emphatic.

هنروح breaks down like this:

• ه = a future marker in Egyptian Arabic
• نروح = we go

So:

• نروح = we go
• هنروح = we will go / we’re going to go

A very common alternate spelling in Egyptian is حنروح. The meaning is the same.

Arabic verbs already include the subject inside the verb form. In نروح, the نـ tells you the subject is we.

So the sentence has we twice in a sense:

• احنا = we
• نروح = we go

This is normal in Arabic. The separate pronoun is often used for emphasis, contrast, or just natural speech rhythm.

In Egyptian Arabic, the verb راح / يروح often takes its destination directly, without needing a separate word meaning to.

So English says:

• go to a party

But Egyptian Arabic can simply say:

• يروح حفلة
• نروح حفلة

This is very natural. Arabic does not always match English preposition-for-preposition.

This is a noun chain, often called an iḍāfa-type structure in Arabic.

• حفلة = party
• عيد ميلاد = birthday

So حفلة عيد ميلاد is literally something like:

• party [of] birthday

In natural English, that becomes birthday party.

Arabic often builds expressions like this by putting nouns next to each other, where the later noun explains the first one.

صاحبي means my friend.

It breaks down like this:

• صاحب = friend / companion
• ـي = my

So:

• صاحب = friend
• صاحبي = my friend

That ـي ending is a very common way to show possession in Arabic.

Because Arabic normally expresses possession by putting the thing possessed first and the owner second.

So:

• عيد ميلاد صاحبي = literally birthday of my friend
• natural English: my friend’s birthday

Then the full phrase is:

• حفلة عيد ميلاد صاحبي
• literally: party [of the] birthday [of] my friend
• natural English: my friend’s birthday party

This word order is very normal in Arabic.

يوم السبت means on Saturday or Saturday.

• يوم = day
• السبت = Saturday

Yes, you could often just say السبت by itself. Both are natural in Egyptian Arabic.

For example:

• هنروح السبت
• هنروح يوم السبت

Both can mean we’re going on Saturday. Adding يوم can make the time expression sound a little fuller or clearer.

The days of the week in Arabic are normally used with الـ:

• السبت = Saturday
• الأحد = Sunday
• الاثنين = Monday

So the الـ here is normal.

As for pronunciation: the letter س is a sun letter, so the l in الـ is not pronounced clearly. Instead, it assimilates to the next sound.

So السبت is pronounced more like:

• es-sabt
• or is-sabt

not al-sabt.

When a word ending in ة is followed by another noun in a connected noun phrase, that ending is often pronounced like -t.

So:

• by itself: حفلة → roughly ḥafla
• in a phrase: حفلة عيد ميلاد → roughly ḥaflet ʿīd milād

That is why learners often hear a t sound there even though the word alone may sound like it ends in -a.

A few things point strongly to Egyptian Arabic:

• احنا / إحنا instead of Standard Arabic نحن
• the future marker ه / حـ in هنروح / حنروح
• the overall everyday spoken structure and vocabulary choice

A more Standard Arabic version would look different, for example using forms like سنذهب or سوف نذهب instead of هنروح.

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