Since the scope of a dissertation is large, at approximately 250 to 300 pages, you should be clear from the outset about your own motivation, the effort and the time to be invested, and be sure that you have both the interest and the stamina to plan, implement and complete the project.
Note the following regarding topic identification:
It is possible that previous academic work (term paper, bachelor's thesis, or master's thesis) may have opened up certain areas of research that could not be explored in that work, however.
Do you already have a preferred field and may you already know some of the existing literature and previous research projects and results? If the topic is unfamiliar to you it’s a good idea to find a writer just for getting some raw drafts and ideas from an expert. If it’s an option for you, read this article about customwritings.com. Remember it’s not the only option, just the one I’ve been using myself.
Consult the research databases of dissertation topics in your field! You should make sure that your topic has not been worked on and submitted as a dissertation before. In each university, each department compiles lists of ongoing dissertations and dissertations completed at the institute. In addition, the catalog of the German National Library lists all German-language dissertations since 1913.
The knowledge of already researched topics helps you with the
precise delimitation and definition of your own research question. The examination of thematically similar dissertations provides first hints for subject-relevant literature research.