Wow, thank you very much for your answer Frey! With your message, you open my eyes!!! so I know what to do and it is exactly what you said. Before I start some certified, I need to be more comfortable with the system, networking, tools, OWASP, etc…
thanks for all your Links, they are already in my ToDo list. 
I just thought it would make sense if I would do first the CEH (because of the theory) and then the OSCP (because of the practice), but this just for the future.