It was
convenient for me to be in these classes when I needed to ask questions, because when the teacher asked 'Are there any questions?' only a few students would raise their hands.---> interesting!
Although today I know more than I did in the past, I still have so many questions.
Now, this is too broad and simple of a statement to put at the end of the first paragraph. At the end of the first para, you should give a fascinating answer to the question, "What don't you know?"
Use commas here:
Although I still want to ask how bacteria hurt my eyes, a college professor at the university told me that
, due to my limited knowledge, I cannot understand the mechanism.
However, the more I know, the more I find unknown. this sentence is a little cliche, and it is poorly worded. I think it is better to leave it out.
I think you should revise this and add several specific, intelligent questions that are related to your intended major. You are off to a good start, though, because you make some excellent observations.