The word fiesta in the second sentence is spelled wrong.
Answer: It looks like you just need to cut off the last vowel (and consonant if there is one) of the word.
For number one, it's "perezosísimo"
For question 2, it's "aburridísimo"
For question 3, I think you do the same but keep it plural, so "interesantísimos" I would imagine.
1. Las
2. La
3. El
4. El
5. El
6. Las
7. El
8. La
3. Quién
Quién means who.. so, who dances really good? Quién baila muy bien ?