how can you find

my name is Jessica Cook. I have a family who is native American. I don't have any contact with and living relative that is in the right state of mind to give me info on that part of my family. how can I find info on them? I can only go back in that family to late 1800.

another question is I am trying to find info on my family in Germany before WWI. they were Jewish and no one on that side of my family is talking to me. so how would I find that?

the last question is there a way that I can restart my family tree. thank you for all your help.