Thank you all of your suggestions!
Recently I'm so frustrated about my singing.
Because I changed my singing teacher, she is new to me and she doubt that if I were a soprano. And she said I sang too dark for my middle and middle lower range which is not good. And she said my notes below middle C is not really impressive. It's seems that I totally lost my direction......
Do I still work with a teacher who is a mezzo-soprano or soprano???