As teachers, we need to educate ourselves by learning while educating our students. If we cease/stop learning and just use what we’ve learned after graduation [The "after graduation" modifier here is a bit confusing. Perhaps rephrase something like, "After graduating (from University), if we just use what we have learned already..."] to teach our students, we absolutely can’t become excellent teachers. We need to learn advanced teaching theories as well as effective teaching methods to make our classes much more lively, interesting and knowledgeable [<-- I would not say a class is "knowledgeable". Rather, a person is. I'm not sure of a better word to suggest. To say what you mean might require rephrasing. Or someone else might have a better word.].

As teachers, we ourselves need to learn as we teach. If we cease learning and just do as we have been trained, we won’t excel as teachers. We need to learn advanced teaching theories as well as effective teaching methods to make our classes lively, interesting and informative. A class can't be "knowledgeable". Only a person can be "knowledgeable". Saying "we ourselves" rather than "we" puts more emphasis on "we". As a matter of style, try to reduce your use of unnecessary emphasizers like "much more", "very", "just", "absolutely" etc.. Allow your words speak for themselves.