New vocabulary practice

Pristine
- I liked the pristine beach that my hometown used to have and feel very sad that many foreign investors have come and built artificial buildings and hotels near it.

Prowess
-That professor's prowess in Chemistry is so high. I can assume it make that assumption as he won a  Nobel Prize (for chemistry?) 2 years ago.

Supersede
-I hope a new boss comes and supersedes the actual the current one. This guy doesn't know anything at all.

Lax
-The teacher was so lax that he couldn't figure out that their students were cheating on the exam.

Ephemeral
-Don´t worry mom, I think this is just an ephemeral fever and I don´t need to take the any medicine

Allude to
- She has never told me that she has a boyfriend, but she alluded to her haveing a date on next Saturday when I talked with her.

Gobble up
-The abandoned dog gobbled up the food when some strangers gave him something to eat.

Your usage of the words was correct, just some of the grammar was slightly off.