The company name is most prominent, then your job title, then your name. I used "shachou" for your job title: this means the man at the top (boss, chairman, proprietor). Your name should be written phonetically and, as your name is German and I'm English, I'm not sure I've got it right. What I have written is pronounced "Ralf Pay-tar Vill-keh" by an English person
The address will be in roman letters, although you could add ドイツ (Doitsu, or Germany) to make it clear where you are.
For the phone, e-mail, fax and so on I think I would use icons because everybody knows what they mean. That is, you would have something like this:-
Ralf-san, マイケルsan, thank you very much for the help, マイケルsan! I was wondering, though, if shachou can match "manager".
Like Michael-san's explained, the title "shachou" means "the person in top of the company" and often translated as "president", someone like CEO, meaning that shachou is in the higher position than anyone in the same company (except there's "kaichou"). If this is not your case, you can also use the word マネージャー [maneejaa].