الشنطة تحت السرير، مش فوق المكتب.

A natural Egyptian pronunciation is:

ish-shanTa taHt is-sarīr, mish fōʔ il-maktab

A few helpful notes:

• الشنطة → ish-shanTa or esh-shanTa
• تحت → taHt; the H is a deep throat sound, not a regular English h
• السرير → is-sarīr
• مش → mish
• فوق → fōʔ; the last sound is a glottal stop, like the break in uh-oh
• المكتب → il-maktab

You may hear small vowel differences depending on the speaker.

In Arabic, present-tense sentences like this usually do not use a verb for is / are.

So:

• الشنطة تحت السرير literally looks like the bag under the bed
• but it naturally means the bag is under the bed

This is completely normal in both Egyptian Arabic and Standard Arabic.

If you wanted was, then you would use a verb:

• الشنطة كانت تحت السرير = The bag was under the bed

In Egyptian Arabic, مش is the very common everyday way to say not in sentences like this.

Here, it negates the location phrase:

• مش فوق المكتب = not above/on the desk

This is especially natural in non-verbal sentences like this one, where there is no written-out is.

A native English speaker can think of it like:

• The bag is under the bed, not on the desk

Because لا is not the most natural negator here in Egyptian Arabic.

In Egyptian:

• مش is the normal choice for negating nouns, adjectives, and location phrases
• لا often means no, or appears in other kinds of expressions

So for this sentence, مش فوق المكتب sounds natural, while لا فوق المكتب would not be the normal everyday Egyptian way to say it.

Because Arabic, like English, often leaves out repeated information when it is already obvious.

Compare English:

• The bag is under the bed, not on the desk

You do not need to repeat the bag is in the second part.

Arabic works the same way here:

• الشنطة تحت السرير، مش فوق المكتب

The listener already knows you are still talking about the bag.

الـ is the Arabic definite article, meaning the.

In Egyptian Arabic, it is often pronounced il- or el-. But its pronunciation changes depending on the next consonant.

In this sentence:

• الشنطة starts with ش
• السرير starts with س

Both ش and س are sun letters, so the l sound of الـ blends into the next consonant:

• الشنطة → ish-shanTa
• السرير → is-sarīr

But المكتب starts with م, which is a moon letter, so the l stays:

• المكتب → il-maktab

So the spelling stays the same, but the pronunciation changes.

شنطة is very common in Egyptian Arabic and sounds colloquial and natural there.

A more formal / Standard Arabic word for bag is:

• حقيبة

So:

• الشنطة sounds everyday and conversational
• الحقيبة sounds more formal or Standard Arabic

Many Arabic speakers outside Egypt will still understand شنطة, but it definitely has a colloquial feel.

They are location words meaning:

• تحت = under / below
• فوق = above / on top of / over

In Egyptian Arabic, they come before the noun:

• تحت السرير = under the bed
• فوق المكتب = on top of / above the desk

They do not change for gender or number in this kind of sentence.

In Egyptian Arabic, فوق is very common for physical location and can cover meanings like:

• on
• on top of
• above
• over

So فوق المكتب is a very natural everyday way to say the thing is on top of or above the desk.

على can also mean on, and you may hear:

• على المكتب

Very roughly:

• فوق often emphasizes above/on top
• على often emphasizes on a surface

But in everyday Egyptian speech, there is overlap, and both can be used in many situations.

It can mean desk or office, depending on context.

In this sentence, because it comes after فوق:

• فوق المكتب

the meaning is clearly desk, because something can be on top of a desk.

If someone said:

• في المكتب

that would often mean in the office.

So context tells you which meaning is intended.

It is mainly Egyptian Arabic / colloquial Arabic.

The strongest clues are:

• الشنطة instead of more formal الحقيبة
• مش for negation, which is very colloquial

Other words in the sentence, like تحت, فوق, سرير, and مكتب, are widely understood.

A more Standard Arabic version might be:

• الحقيبة تحت السرير، وليست فوق المكتب

Yes. شنطة is a feminine noun.

You can often tell because it ends in ـة.

In this specific sentence, gender does not create any visible change, because there is no adjective or past-tense verb agreeing with it. But if you replaced the noun with a pronoun, you would use the feminine pronoun:

• هي تحت السرير = It is under the bed
  literally she is under the bed

So it does matter grammatically, even though this sentence itself does not show much agreement.