1. My favourite writer, whose books are always unpredictable, is Carlos Ruiz Zafón. (Make sure there is a comma after the word "unpredictable.")
2. It is not very easy to learn how to windsurf.
3. This is the teacher who always makes us laugh.
4. This is the bookshop where you can buy travel books and maps.
(for #4, you could also use "in which" instead of "where," but both are correct.)
5. I don't mind helping my mum with the housework
TASK TWO:
1. to take
2. to spend
3. studying
4. breaking
5. doing
TASK FIVE:
1. based
2. addict
3. television (or "TV." TV is a shorter way to say "television.")
4. skim
5. interview
I'm sorry, but I cannot help you with the rest.
Good luck, though! <3