Q: Are we new souls?
A: Baal HaSulam writes in the article, "The Freedom", that each generation consists of the souls of the previous generation, but in new bodies. This is how mankind evolves. Souls accumulate experience from generation to generation, so that everything we study as scientific discoveries in this generation, and all experience and knowledge that is acquired is imprinted in the next generation as an obvious, indubitable fact. That is why children are smarter than their parents.
Indeed, there is reincarnation, but certainly not for bodies. The souls are what return, but only in the human body. The process of reincarnation can be understood only by attaining the Upper World, by studying Kabbalah. In the Upper World, souls without bodies are tied to the Kabbalists, who are not burdened by the body and can exist in our world and in the spiritual world simultaneously. Therefore, the laws and actual attainments of reincarnation are only open to Kabbalists.