Relative pronoun and clauses

1- The beach is a place that I go to if I am feeling a little depressed and it always makes me feel better.
2- Kamelia, who is one of my closet friends, always know how to console me.
3- Poligamy is a notion that I will never be able to accept.
4- An old ring, which is probably my most treasured possession, was given to me by my grand mother.
5- Few people have heard of Hicham Elgerouj who is a runner, but he is very famous in my country.
6- London which I've always dreamed of visiting, now seems to me like any other city.