1. That tree is an oak. My grandfather planted it 60 years ago.

->That tree, which my grandfather planted  60 years ago, is an oak.
2. Tina and Charlie are having a party this Saturday. They’re identical twins. 
-> Tina and Charlie who are identical twins,are having a party this Saturday.
3. On the Friday, we spent most of the day sitting in the port. On the Friday, the ferry was delayed.

-> On the Friday, when the ferry was delayed,we spent most of the day sitting in the port.
4. Barbara used to work in the Personnel Department. You met her at Libby’s last Thursday.
 -> Barbara, who you met at Libby’s last Thursday,used to work in the Personnel Department.
5. Let’s go to da Vinci’s. They do a great pepper steak there.
->Let’s go to da Vinci’s where they do a great pepper steak.

6. This book was once owned by Sir Francis Drake. It was given to me by my great aunt.
 ->This book wwhich it was given to me by my great aunt was once owned by Sir Francis Drake.
7. Why did Danny decide to enter the marathon? Danny’s totally unfit.
 ->Danny's totally unfit, that's the reason why she decided to enter the marathon.
8. Guy is now engaged to my sister. His sister is married to my brother. 

->Guy, who's sister is married to my brother, is now engaged to my sister.

1. That tree whom my grandfather planted 60 years ago is an oak

2. Tina and Charlie who are identical twins are having a party this Saturday

3.we spent most of the day sitting in the port On the Friday when the ferry was delayed.

4,Barbara whom You met at Libby’s last Thursday used to work in the Personnel Department

5. Let’s go to da Vinci’s where They do a great pepper steak

6. This book which was given to me by my great aunt was once owned by Sir Francis Drake

8.  Guy is now engaged to my sister whose sister is married to my brother