Account username and password don't match on mac users & group on Mac
You need an admin user to manage this Mac, so why not create that first:


New MacBook had user accounts already; I deleted admin and can&#39;t get back in


I like my answer on that post (go figure) and then you can use the new admin credentials to fix your current user short name and home folder. 

Lots of other good advice and answers here as well:


I don&#39;t have administrator account on my mac