Jewish Question

I asked this in the comments section of a previous post: Hopefully I can get some answers.

If Jewishness passes from mother to child, because we may not know who is the actual dad, then why does tribal lineage, especially priesthood (kohaniim, leviim) pass down from father to son?

How do we know who is the dad?

What if the son is really the child of the gardner or milkman or neighbor or other?

If Jewishness passes down from the mother because we may not know who is the dad, how could we possibly expect that the tribal lineage passed down truthfully?