אם תאבד את מספר הטלפון שלה, יהיה קשה לחדש את הקשר.

In Hebrew, a real future condition is commonly built with אם + future.

So:

• אם תאבד = if you lose
• יהיה קשה = it will be difficult

This is different from English, which usually says if you lose, not if you will lose.
Hebrew is more literal here: both parts can point to the future.

So the pattern in this sentence is very normal:

• אם
  • future verb
• then a future result

תאבד is most naturally you will lose addressed to one male person.

So:

• תאבד = you (masculine singular) will lose

If you were speaking to a woman, it would usually be:

• תאבדי

One important detail: without vowel marks, תאבד can also look like she will lose, but in a normal learner context it is usually understood from the meaning and situation.

Here את is the marker of a definite direct object. It does not mean you in this sentence.

Hebrew uses את before a direct object when that object is definite, for example:

• את הספר = the book
• את מספר הטלפון שלה = her phone number

So in this sentence:

• תאבד את מספר הטלפון שלה
• literally: you will lose [direct object marker] her phone number

Because her phone number is a specific, definite thing, את is required.

This phrase means her phone number.

Breakdown:

• מספר = number
• הטלפון = the telephone / the phone
• שלה = hers / her

So literally it is something like:

• the number of the phone, hers

But natural English is simply:

• her phone number

Hebrew often expresses possession with שלה / שלו / שלהם and similar forms after the noun phrase.

Hebrew has more than one way to show possession.

Here, possession is shown with the separate possessive word:

• שלה = hers / of her

So:

• מספר הטלפון שלה = her phone number

This is a very common and natural structure in modern Hebrew.

In some cases, Hebrew can use attached endings or construct forms, but for everyday speech, noun + שלה / שלו / שלהם is extremely common and easy to use.

יהיה קשה literally means will be difficult.

Breakdown:

• יהיה = will be
• קשה = difficult / hard

Hebrew often uses this kind of impersonal structure:

• קשה ל... = it is difficult to...
• יהיה קשה ל... = it will be difficult to...

So:

• יהיה קשה לחדש את הקשר
• it will be difficult to renew the contact/relationship

This is a very common pattern in Hebrew.

Because it comes after קשה in the pattern:

• קשה + infinitive
• difficult + to do something

So:

• לחדש = to renew
• יהיה קשה לחדש = it will be difficult to renew

This is like English difficult to restore / difficult to renew / difficult to restart.

The ל־ here is the normal infinitive marker, often equivalent to English to.

לחדש את הקשר is an idiomatic phrase meaning:

• to renew contact
• to reestablish contact
• to reconnect
• sometimes to resume the relationship/contact

Breakdown:

• לחדש = to renew / restore
• הקשר = the connection / the contact / the relationship

So the phrase does not necessarily mean a romantic relationship. It can simply mean getting back in touch with someone.

The noun קשר can mean several related things, depending on context:

• connection
• contact
• relationship
• sometimes even tie or link

In this sentence, because it talks about losing someone's phone number, הקשר most likely means:

• contact
• or the connection between you and her

So לחדש את הקשר is best understood as to get back in touch or to reestablish contact.

The ה־ is the definite article, meaning the.

So:

• קשר = connection / contact
• הקשר = the connection / the contact

Hebrew often uses the definite article in places where English may sound more natural without it. Here, the idea is that there is a specific existing connection between the people, so הקשר is definite.

That is why Hebrew says:

• לחדש את הקשר

rather than just:

• לחדש קשר

The definite version sounds more natural for renewing contact with a specific person.

Yes. Hebrew can also put the result clause first:

• יהיה קשה לחדש את הקשר אם תאבד את מספר הטלפון שלה.

This means the same thing:
It will be difficult to renew contact if you lose her phone number.

Putting the אם clause first is very natural, and putting it second is also natural. The choice often depends on what the speaker wants to emphasize first.