Suhina D. answered 06/18/19
Private Bay Area Science Tutoring
There are two grammatically appropriate edits to this sentence. You could say "After one year, I quit my job, said goodbye to my friends, and went to Beijing to study philosophy. There, I participated in a lot of classes taught by professors, but I was never registered as a formal student." Alternatively, you could say, "After one year, I quit my job, said goodbye to my friends, and went to Beijing, where I attended philosophy classes but did not register as a formal student." This is grammatically correct but I do not recommend it since some clarification about the classes being taught by professors is lost.