"look sharp" means pay attention and act quickly, often to try to impress that you aren't being lazy.
"Quick! The boss is coming! Look sharp!"
"make light of" means to not take something too seriously, to see the funny side of something
"My mother made light of the fact that I had forgotten my keys. I had expected her to be angry but she just laughed and said I would forget my head one day."
- For Teachers