Complex sentence: Total depravity does not mean that people have lost part of their humanity or are ontologically deteriorated, because Adam and Eve were created with the ability to not sin, and people retain that essential nature, even though the properties of their humanity is corrupted.
Split into simpler sentences: Total depravity does not mean that people have lost part of their humanity or are ontologically deteriorated. Just as Adam and Eve were created with the ability to not sin, people retain that essential ability to either sin or not sin, even though some properties of their humanity is corrupted.