Doubts and questions about ghusl

Asalam alaykum brothers and sisters I recently did ghusl but I am having doubts of whether I reached every part of my body with water. I am almost certain that water reached every part of my body but I am unsure whether I scrubbed every part perfectly. Also, since the hands can not reach all parts of the back, what should one do in this situation? I tried my best to get water back there and am pretty sure I covered it but I am still asking. Jazak Allah