Here are the sentences joined using defining or non-defining relative clauses:
1. My girlfriend, who has taught me a lot, is a teacher.
2. The doctor who cured the Chief Executive of pneumonia is famous.
3. The man who runs 2 km every day is a fireman.
4. My father, who is very hardworking, is a merchant.
5. Jolie's boyfriend, who is so stupid, asked for help.
6. The boy who sings sweetly has a good voice.
7. Kelly Chan, who is a famous singer, is the woman.