5) не знаю.

6) thin - thiner - thinest

difficult - difficulter or more difficult - difficultest or most difficult

bad - wors - worst

nice - nicer - nicest

boring - more boring - most boring

good - better - best

7) 2. most intelligent

3. most expensive

4. younger

5. most beautiful

6. shorter

7. more crowded

8. oldest

9. earlier

10. most famous