How can I delete my tree and start over? It is very mixed up and incorrect ?
Marilyn Fischer_2 That is more of a question for Ancestry or some other site where you actually do have a tree. In FamilySearch there is only one world tree. I understand the conundrum of mixed up ancestors, some correctly placed, and others not. If I were you, I would start at the lowest level and disconnect the incorrect people. This will create floating branches, it won't delete their information. Make sure you have sources to back up the fact that these people were incorrectly attached so you can put that in the reason statement. "This person lived in California according to 1900 census, my relatives were never in that state" something like that. Also, that may disconnect some correct branches that are latched on, but that is ok, you can later reconnect those back where they belong. After you disconnect the incorrect people, search to find, or create records for the correct people. Ensure sources are correct as much as you can find. When you get to the points where you know there is a correct branch out there that needs a new connection point, search for it and attach it.
This is a labor of love and everyone will benefit from your work!
I tell people who want to know where to start to "prove" the information found in the Tree. Start close to you and find all of the sources and proof for one person, their spouse and their children. After you have gotten that all sourced, move to one of the parents and do the same thing for the family where they are a child. Repeat with each family. This way you can verify that information in the Tree is correct and nobody is missing in the each family.