For some reason my user account has both my old and new email addresses. I can sign in with my a) user name b) old email and c) new email. Now my premium account is only connected to the new email so if I sign in using a) or b), I can´t access the premium account.
I tried logging in with a) and b) to take out the old email permanently and replace it with the one that I use but it wasn´t possible. When typing the new email it says "this email is already in use".
Is there any way to get rid of all these ghost accounts and start all over with one email connected to the Spotify account?
According to what you're letting us know, it's possible that you have more than one Spotify account associated to you. If you'd like, you can find some useful information on how to locate additional Spotify accounts on this page.
Once you've found them, our best suggestion would be for you to close them with the steps you'll find here.