في غبار كتير عالرف، ولازم امسح الرف اليوم.

Here في means there is / there are.

So في غبار كتير عالرف literally has the structure there is dust a lot on-the-shelf.

Important: in this sentence, في is not the preposition in. It is being used existentially, to say that something exists somewhere.

غبار means dust, and كتير after a noun often means a lot of / much in Levantine.

So:

• غبار كتير = a lot of dust
• literally: dust much/a lot

This is very natural with mass nouns like غبار, مي, شغل, etc.

Also, كتير is a very common Levantine word. In Standard Arabic, you would more often see كثير.

عالرف is a colloquial contraction of على الرف.

So it breaks down like this:

• على = on
• الرف = the shelf
• على الرف → عالرف in everyday Levantine writing and speech

This kind of contraction is very common in spoken Arabic.

Because ر is a sun letter.

When ال comes before a sun letter, the ل sound assimilates to the next consonant in pronunciation.

So:

• written: الرف
• pronounced: roughly ar-raff or er-raff, depending on accent

And with على reduced in speech:

• على الرف → عالرف
• pronounced roughly ʿar-raff

The spelling keeps the ل, but the pronunciation usually does not.

لازم here means must, have to, or need to.

It is one of the most common ways in Levantine to express necessity:

• لازم امسح الرف اليوم = I have to wipe the shelf today

A useful pattern to remember is:

• لازم + imperfect verb

Examples:

• لازم روح = I have to go
• لازم نام = I have to sleep
• لازم امسح = I have to wipe

Because after لازم, Levantine normally uses the bare imperfect without بـ.

So:

• بمسح = I wipe / I am wiping / I usually wipe
• لازم امسح = I have to wipe

The b- prefix is common for normal present or habitual meaning, but after words like لازم, it usually drops.

So لازم امسح is the natural form.

Because Arabic verbs already contain subject information, so the pronoun is often omitted.

In this sentence, امسح is understood as I wipe / I should wipe from the grammar and context.

So:

• لازم امسح الرف اليوم = I have to wipe the shelf today
• أنا لازم امسح الرف اليوم = also possible, but more emphatic

One extra note: امسح can also look like an imperative form in isolation, but after لازم the meaning is clearly I have to wipe, not a command.

Repeating the noun is very normal in Arabic, especially for clarity.

So:

• ولازم امسح الرف اليوم = and I have to wipe the shelf today

You could also say:

• ولازم امسحو اليوم = and I have to wipe it today

Both are possible. Repeating الرف just makes the sentence a little clearer and more explicit.

These are two sounds English speakers usually need to practice.

• غ in غبار: a voiced sound made at the back of the throat. It is often compared to the French or Parisian-style r.
• ح in امسح: a strong, breathy h sound from deeper in the throat than English h.

A rough pronunciation guide:

• غبار ≈ ghbar
• امسح ≈ emsaḥ

The final ḥ in emsaḥ is not the normal English h. It is stronger and produced lower in the throat.

Yes, it sounds clearly colloquial and very natural in Levantine.

Some Levantine features here are:

• كتير instead of Standard كثير
• عالرف instead of fully pronounced على الرف
• لازم امسح as a spoken-style necessity structure

A more Standard Arabic version could be:

• يوجد غبار كثير على الرف، ويجب أن أمسح الرف اليوم
• or هناك غبار كثير على الرف، ويجب أن أمسح الرف اليوم

So the meaning is the same, but the sentence you were given is the kind of Arabic you would actually hear in everyday Levantine speech.