Sorry if I misunderstand your question. I don’t think that dreams can give knowledges. A dream can help to solve a problem encountred in real life because is the expression of the brain working on the problem during sleep, but knowledge can not derive from a dream.
I intend knowledge as the sum of all informations that each individuals accumulates during life. Dreams can help to solve problems, can help to create stories and genial discoveries, but cannot give knowledge.
An exception can be future prevision, because a dream allow to know exactly what will happen. But does it really exists?
These are only my opinions, don’t take that as statements.