המספר ששלחת לי לא מספיק מדויק, ולכן קשה להבין אם הוא קשור לכתובת הזאת.

Because המספר means the number, with the definite article ה־ attached to the noun.

In Hebrew, ה־ is the equivalent of English the:

• מספר = a number / number
• המספר = the number

So המספר ששלחת לי means the number that you sent me.

ש־ is a very common Hebrew word meaning that, which, or who, depending on context.

So:

• ששלחת לי = that you sent me

This is a relative clause, like in English:

• the number that you sent me

You can think of it as:

• המספר = the number
• ששלחת לי = that you sent me

In more formal Hebrew, you might see אשר שלחת לי, but in everyday Hebrew ש־ is much more common.

Because לי means to me, and the verb לשלוח usually works with an indirect object introduced by ל־.

So:

• שלחת לי = you sent to me / you sent me
• שלחת אותי would mean you sent me in the sense of you dispatched me somewhere, which is a completely different meaning.

Examples:

• שלחתי לך הודעה = I sent you a message
• הוא שלח לי קובץ = he sent me a file

So in your sentence, ששלחת לי correctly means that you sent me.

Here מספיק means enough.

So:

• מדויק = precise / exact
• מספיק מדויק = precise enough
• לא מספיק מדויק = not precise enough

This is a very common Hebrew pattern:

• לא מספיק גדול = not big enough
• לא מספיק ברור = not clear enough
• לא מספיק מהר = not fast enough

So המספר ... לא מספיק מדויק means the number ... is not precise enough.

Because it describes המספר, and מספר is a masculine singular noun.

Hebrew adjectives agree with the noun they describe in gender and number.

So:

• מספר is masculine singular → מדויק
• כתובת is feminine singular → if you described it, you would use מדויקת

For example:

• מספר מדויק = an exact number
• כתובת מדויקת = an exact address

ולכן means and therefore, and so, or simply therefore.

It is made of:

• ו־ = and
• לכן = therefore / so

So:

• ..., ולכן קשה להבין ... = ..., and therefore it is hard to understand ...

It is a connector showing result or consequence.

Hebrew often uses an impersonal structure where English uses it is....

So:

• קשה להבין literally = hard to understand
• natural English = it is hard to understand

The word it is usually not stated in Hebrew in this kind of sentence.

Other similar examples:

• קל לראות = it is easy to see
• חשוב לדעת = it is important to know
• מותר להיכנס = it is allowed to enter

So קשה להבין is a very normal Hebrew way to say it’s hard to understand.

Yes, אם often means if, but it can also mean whether.

In this sentence, it means whether:

• קשה להבין אם הוא קשור לכתובת הזאת = it is hard to understand whether it is related to this address

This is very common in Hebrew. Context tells you whether אם means if or whether.

קשור ל־ means connected to, related to, or associated with.

So:

• קשור לכתובת = related to the address
• קשור לבעיה = related to the problem
• זה לא קשור = that’s not related / that has nothing to do with it

Notice the preposition ל־ after קשור. Hebrew requires that preposition here.

The pronoun הוא means it/he, and here it refers back to המספר.

Hebrew often includes the pronoun in this kind of clause:

• אם הוא קשור לכתובת הזאת = whether it is related to this address

Since מספר is grammatically masculine singular, the pronoun is הוא.

In English, number is a thing, so we say it. In Hebrew, nouns have grammatical gender, so a masculine noun takes הוא.

In Hebrew, demonstratives like this usually come after the noun.

So:

• הכתובת הזאת = this address
• המספר הזה = this number
• הספר הזה = this book

Also, זאת agrees with כתובת, which is feminine singular.

So the pattern is:

• noun + demonstrative
• and both are definite

That is why Hebrew says הכתובת הזאת rather than זאת כתובת in this context.

Because in Hebrew, when you say this/that + noun, the noun is usually definite, and the demonstrative itself is also definite in meaning.

So:

• כתובת = an address
• הכתובת הזאת = this address

This is the normal Hebrew structure:

• הילד הזה = this boy
• העיר הזאת = this city
• הדברים האלה = these things

It may feel redundant to an English speaker, but it is standard Hebrew grammar.

Yes, it absolutely can mean a phone number, but the exact meaning depends on context.

מספר can mean:

• a number
• a phone number
• a street number
• a numerical figure

Because the sentence continues with קשור לכתובת הזאת, the speaker probably means some kind of identifying number that is supposed to match or clarify an address, not just a random number.

So Hebrew leaves it as המספר, and context tells you what kind of number is meant.