The doctoral regulations state that a dissertation will not be accepted if it has already been published in its entirety. In exceptional cases, the Promotionsausschuss (PhD board) may, upon recommendation of the Promotionskommission(PhD committee), accept already published parts as part of the dissertation.
Furthermore, the following applies: Content of your dissertation that has already been published may not be included in the dissertation in the same wording. If you publish findings that are also relevant to your dissertation in advance and elsewhere, indicate the additional publication in a footnote within the dissertation and refer to the emerging dissertation within the publication. This will help you avoid self-plagiarism. The key is to avoid using the same wording.