How do you edit or delete text in a tableView?

I am trying have the user to modify/delete default text in a tableview, I have tried the following code witch works but as soon as the user goes to the other view controller and back (or leaves the app and comes back), the text goes back to being the default text. How could I have it work? I have posted the entire code for the tableView so you can have an overview of what I could have done wrong. thank you !I am trying have the user to modify/delete defa