he althought she might run out of cash. She took the bank card with her (case)
----> She took the bank card with her in case she ran out of cash. 
that is the woman. Her daughter has studied abroad (whose)
----> that is the woman whose daughter has studied abroad 
I borrowed her this book. this book is very interesting (which)
--->I borrowed her this book which is very interesting
success depends on your hard work
----> the harder you work, the more successful you will get.
I have difficultly in contacting him
---> I find contacting him difficult.
John is a famous writer. His novels are very interesting (whose)
----> John whose novels are very interesting is a famous writer.
no one has a key. we can't get into the house (can)
---->we can get into the house unless someone has a key.

She althought she might run out of cash. She took the bank card with her (case)

---->She took the bank card with her in case she ran out of cash.

That is the woman. Her daughter has studied abroad (whose)

---->  That is the woman whose daughter has studied abroad 

I borrowed her this book. this book is very interesting (which)

---> I borrowed her this book which is very interesting

success depends on your hard work

----> you work harder ,  the more successful you will get

the harder I have difficultly in contacting him

--->I find contacting him difficult.

I find John is a famous writer. His novels are very interesting (whose)

----> John whose novels are very interesting is a famous writer.

No one has a key. we can't get into the house (can)

---->we can get into the house unless someone has a key.