معجون السنان خلص، ولازم اشتري معجون جديد النهارده.

In Egyptian Arabic, words that start with أ in Modern Standard Arabic are often simplified in speech. So الأسنان becomes السنان in everyday Egyptian pronunciation, and people often write it that way informally too.

So:

• معجون الأسنان = more formal / MSA-style
• معجون السنان = natural everyday Egyptian

Both mean toothpaste.

Here, خلص means ran out, finished, or is gone.

It is the past tense form, and it matches معجون because معجون is singular and masculine. So معجون السنان خلص literally has the structure the toothpaste finished / ran out.

In Egyptian Arabic, خلص is very common for things being used up, ending, or being over.

Because Arabic usually does not need a separate word like it when the noun is already stated.

In English, you might think of:

• The toothpaste ran out not
• The toothpaste it ran out

Arabic works the same way here. The subject is already معجون السنان, so no extra pronoun is needed.

لازم means necessary, and in everyday Egyptian it is very often used to mean I have to, I need to, or must.

So:

• لازم اشتري = I have to buy
• لازم أروح = I have to go

It is one of the most common ways to express obligation in Egyptian Arabic.

In careful spelling, many people would write أشتري. In casual Egyptian writing, especially texting or informal dialogue, the initial أ is often omitted, so اشتري is very common.

So these are basically the same here:

• أشتري
• اشتري

The pronunciation still includes that first-person sense of I buy / I should buy.

This is a very common learner question.

In Egyptian Arabic, بـ often marks the ordinary present tense, especially for habits or ongoing actions:

• بشتري = I buy / I’m buying

But after words like لازم, Egyptian usually uses the verb without بـ:

• لازم أشتري = I have to buy
• not usually لازم بشتري

So in this sentence, dropping بـ is exactly what you expect after لازم.

Because in Arabic, adjectives normally come after the noun they describe.

So:

• معجون جديد = new toothpaste
• literally toothpaste new

This is the normal word order in both Egyptian Arabic and Modern Standard Arabic.

Because معجون is grammatically masculine, so the adjective must also be masculine.

That gives:

• معجون جديد = masculine
• شنطة جديدة = feminine

Arabic adjectives agree with the noun in gender, and usually also in number and definiteness.

النهارده means today, and yes, it is a very common Egyptian Arabic word.

A few useful comparisons:

• النهارده = Egyptian Arabic today
• اليوم = Modern Standard Arabic today
• دلوقتي = now / right now, not exactly the same as today

So النهارده is the natural everyday Egyptian choice in this sentence.

In Egyptian Arabic, ج is usually pronounced like g in go, not like the English j in job.

So:

• جديد sounds roughly like gedeed
• معجون sounds roughly like maʿgoon

This is one of the most noticeable pronunciation features of Egyptian Arabic.

The ع is a consonant that does not exist in English. It is a deep throat sound, often represented in transliteration as ʿ.

So معجون may be written something like maʿguun.

At a beginner stage, the most important thing is:

• notice that the sound is there
• try not to replace it with a strong English consonant
• don’t worry if it is not perfect yet

Egyptian speakers are very used to learners finding ع difficult.

Yes. A more formal or more Standard-Arabic-style version would be:

نفد معجون الأسنان، ولا بد أن أشتري معجونًا جديدًا اليوم.

Compared with your original sentence:

• نفد is more formal than خلص
• الأسنان is the standard form instead of السنان
• ولا بد أن is more formal than لازم
• اليوم is more formal than النهارده

Your original sentence sounds much more natural for everyday Egyptian Arabic.