Hello, teacher. Please allow me to do a little bit correction to your writing. ( I find myself actually wondering what you teach at school)

China Agricultural University (you say Bank of China, so you should say Agricultural University of China.) & China's Youth Day

In (I'd suggest using "on" because you are talking about a time period of a particular day.) the evening of China’s Youth Day. I went to the sports ground of CAU, where a big party was being held. Singers sang and dancers danced (you need to use the past continuous tense here because you are describing what was happening at that time; Singers were singing and dancers were dancing). Many students went (were) jogging along the athletic track. I enjoyed the performances very much.
Occasionally, (You are doing a mental translation from chinese to english in the course of writing.)  I spotted several students were playing (better use "doing") rock climbing. The edge of the cliff, where the angle is over 90 degree (degrees) in many place(s), is very steep. They tried their best to climb as high as possible. It’s a kind of sports which full of stimulation and challenge. It’s an impossible mission for me to climb even only 3 meters, not to mention climbing to the top of the cliff.
Although China’s Youth Day is not suitable for me whose age is around 40. I’m very industrious, hard-working and enterprising. (the underlined part is very Chinglish, honestly. The syntax is very unnatural and thus needs improving.)! For me, I have every reason  looking (to look) forward for a more bright (brighter) future.