Saving Information So Program Remembers Next Time User Signs In

i want the user to login, and the first thing is, having the text document for that(if theres a safer way to do it, let me know) then it goes to the weekly sales page, but theres also the goals for the sales, which rarely change, but if they do i would like them to be able to change them, then next page is the list of the workers, and if they need to i would like them to be able to add workers. so my question is: is there anyway that maybe i could save both the goals, and the workers in the text document, and when they need to change it/add workers it will save it in the text document and the next time they sign in the changes will be permanent? also is there a way to delete the user once they have been created, other than going into the txt document and deleting it.