http://www.ndcnc.gov.cn/libpage/gjtd/index.htm
you can learn all you wanted.
When you hear the opera aria, don't focus on the lyric. If you know it, it is good. If you don't know it, it is good too. Just learn it as a voice art, like you learn the Orchestra which may include Voilins, Cello, drum and so on. Just treat the voice as a instrument. If so, you really enter a higher realm. Pls enjoy it.