1. They were served by a rude and foolish waitress. ( who )
They were served by a waitress who rude and foolish.
2. The furniture in my summer house is in bad shape and need replacing. ( which )
The furniture in my summer house, which is in bad shape, need replacing.
3. I will tell you my secret when you promise not to tell it anybody. (if)
If you promesi not to tell it anybody, I will tell you my secret.

Galiba böyle.