صندوق الرمل في الحمام من ساعة ما جبناه.

Because this is a present-tense nominal sentence. In Egyptian Arabic, you usually do not say a separate verb for is/are in sentences like this.

So:

• صندوق الرمل في الحمام
  literally looks like the litter box in the bathroom
• but it naturally means The litter box is in the bathroom

The sense of has been comes from the time expression من ساعة ما جبناه, which adds the idea of since we brought it.

من ساعة ما is a very common Egyptian expression meaning since or more literally from the time that.

Word by word:

• من = from
• ساعة = hour, time, moment
• ما = a connector before the following clause

So here من ساعة ما جبناه means since we brought it.

Also, ساعة here does not mean a literal 60-minute hour. It means something more like the moment or the time.

In Egyptian Arabic, ما often appears in time expressions before a full clause. It helps connect the time phrase to what comes after.

So:

• من ساعة ما جبناه = since we brought it
• بعد ما وصل = after he arrived
• أول ما شافني = as soon as he saw me

You can think of this ما as part of a common spoken pattern, not as a separately translated word every time.

جبناه breaks down like this:

• جبنا = we brought
• -ه = him / it

So جبناه means we brought it.

The verb is from Egyptian Arabic جاب = he brought.
When it is conjugated, the form changes:

• جاب = he brought
• جبت = I brought
• جبنا = we brought
• جبناه = we brought it

It refers to صندوق الرمل as a whole, meaning the box.

The important thing is that Arabic agreement follows the head noun, which here is صندوق. Since صندوق is masculine singular, the pronoun is -ه.

So even though the phrase contains الرمل, the pronoun refers to the box, not the sand.

Because this is an iḍāfa construction, often called a possessive or noun-link construction.

In an iḍāfa:

• the first noun usually does not take ال
• the second noun can be definite
• the whole phrase can still be definite

So:

• صندوق الرمل = literally box of the sand
• in natural English, this becomes the litter box or the sand box, depending on context

That is why صندوق does not have ال here.

Because in an iḍāfa, definiteness is determined by the last noun.

Since الرمل is definite, the whole phrase صندوق الرمل becomes definite too.

So although صندوق looks indefinite by itself, صندوق الرمل as a unit is definite.

This is a very common Arabic pattern.

Because the sentence first gives the main situation, then adds the time frame.

So the structure is basically:

• صندوق الرمل في الحمام = the litter box is in the bathroom
• من ساعة ما جبناه = since we brought it

That order is very natural in Egyptian Arabic.

You could move the time phrase for emphasis, but the original order sounds like a normal everyday statement.

Yes, الحمام can mean different things depending on context.

Common meanings include:

• bathroom
• bathhouse
• pigeons / doves

In this sentence, because of في الحمام and the household context, it clearly means in the bathroom.

So this is one of those words where context matters a lot.

In Egyptian Arabic, ج is usually pronounced like a hard g as in go.

So جبناه is pronounced with a g sound, not like the English j in job.

A rough pronunciation would be:

• gibnaah or gebnaah

You may see slightly different transliterations, but the important point is the hard g.

Because ر is a sun letter. In Arabic, when ال comes before a sun letter, the l sound assimilates to the next consonant.

So:

• written: الرمل
• pronounced: ir-raml or er-raml

The r sound gets doubled.

This is a pronunciation rule only; the spelling stays the same.

Yes, it sounds very Egyptian, especially because of:

• من ساعة ما for since
• جاب / جبناه for brought
• the overall spoken style

A more MSA-like version could be:

• صندوق الرمل في الحمّام منذ أن أحضرناه
• or صندوق الرمل في الحمّام منذ أن جلبناه

So the original sentence is perfectly natural in Egyptian Arabic, while those alternatives sound more formal and standard.