I will graduate from Brighture at June 30. I do not want to regret that I came here, so I have to improve my English skill. Therefor, I do not mind that my face just a little bit become rough skin due to not enough sleeping. 听起来自然吗？

i understand, but it is a little confusing. i think you mean, "i will graduate from Brighture on June 30th. i want to make use of my time here, and improve my english (this could be rewritten differently) I have learned to be thick skinned, and work without getting enough sleep.

this is just one way you could say this.

if you have questions i can try to help.:) i'm sorry if this was confusing.