Perhaps this will help you regarding what a primary, secondary, and tertiary source is:
Regarding bias and authors, everyone has one, but good historians tend to downplay it as much as possible, others do not. What is called for is a judicious evaluation of source material which is something that is taught in masters programs in history, beginning with a course on historiography.
The idea that secondary sources are not evidence is incorrect. A blend of primary and credible secondary sources is an excellent way to conduct research and historical inquiry. The product of that methodology should be a solid secondary source that can be used by others for their work.