The first is correct. The second is unnatural for me.
Student or Learner
Please tell me whether the following sentences are both correct. Thank you.
A) What percentage of the students are overweight?
B) How many percent of the students are overweight?
For the second, I might use "What percent of the student population is overweight?"
For "How many percent ...", the only natural question I can think of is "How many percent of 90 is 15?"
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.