In most subject areas, an assistant doctorate is the traditional way to earn a doctoral degree in Germany. With this path to a doctorate, you are employed as an academic assistant in the department or institute, and closely involved in research and teaching.
In addition, as a teacher and supervisor for student work, you are responsible for students. That gives you significant on-the-job skills, and it is not uncommon to be involved in externally funded projects.
You develop your dissertation topic together with your dissertation supervisor (usually the department chair or institute head), who supports you in your academic development.