Do reincarnation and karma provide answers to apparent injustices in life? What is the purpose, logic, and justice of reincarnation and karma?

How did we end up in this life and these living conditions? By chance, bad luck, fate, your parents or a higher power? Or do we choose to reincarnate and determine by means of karma where and with whom we reincarnate? Do we as humans have a one-time existence? Or does part of us survive after death? If so, which part?

What role do reincarnation and karma play in our lives and how can we become the directors of future lives?