Could you please correct my cover letter. I think there's a lot of mistakes. Thank you in advance.

Dear "Center"
I am a 4th year medical student at"My school". interested in participating in clinical electives at "Center" . I firmly believe that "Center" which is one of the best liver center in the world has the excellent care and treatment in cancer patients in order to inspire me about taking care of cancer patient for my future career as a good doctor .
When I was a 3rd year medical student which is the first year in clinical practices,I was really excited . For sure, I was excited about New world in Hand-on experiences not just in the textbook. I was excited to learn new disease and treatment in everyday. I really enjoyed in helping sick patient. In oncology unit , I had been assigned for taking care of many cancer patients. One of my patients had liver cancer which is I barely knew about how to take care of him at that times. He really suffered from his disease that made his abdomen full of fluid so that he couldn't sleep even in sitting position because of marked ascites. This made me feel sympathy. I would like to help him better. I would like to see him less suffer. From that day, I was interested in art and science of oncology. It's one of medical branch that is always hard to understand,That's why it's so challenging me. Participating in clinical electives at "Center" will definitely make me understand this field better. That's reason I choose the electives in this great center.
I strongly believe that I will be a good fit in this elective course. Thank you for considering my application.