The problem with do-it-yourself training for classical singing is that you can't see and hear what you are doing wrong or have the expertise to evaluate what you are doing right or wrong. This leads to habits that can damage your voice, even if you are hitting the notes you want to hit.

As others on the thread have said, this genre of singing needs the coaching of a good teacher. My concern is for your vocal health. The voice is a delicate instrument. I know of singers in choirs who are certainly hitting notes of the score, but they are pushing to get volume or straining and will eventually develop nodes or other problems. Take care.