I'm a native speaker from Germany (Standard German accent). For my graduation from school (Abitur) in 2006, I chose German as an advanced course. Since 2008 I've been working as a professional writer.
I can help you to improve your ability to speak proper German. We could talk or learn a beautiful poem, or try to reduce your accent or work on your vocabulary. You just need to tell me about your personal goal.
Books I recommend are:
*** Beginner / Intermediate *** "em Übungsgrammatik" (ISBN: 978-3-19-007657-0): grammar explanation with exercises and answer key
*** Intermediate / Advanced *** "Deutsch: Sag's besser Teil 1" (ISBN: 978-3-19-007453-2): grammar and rephrasing exercises (with answer key)