Try to assign a department or a discipline to the topic of your dissertation thesis.
The complete list of the departments of Freie Universität may be found here.
Click on the link to the department on the list that seems most likely to comprise your discipline. A new list opens, presenting all institutes and disciplines assembled under the roof of the department.
Chose an institute or discipline and go to the respective homepage. Large institutes / disciplines are subdivided into research or working areas, which are accessible from the page you are actually on. Smaller institutes instead provide direct links to the professors of the institute along with a short description of their specific research interests.
Chose those persons or working areas from the list which seem relevant to you. At this stage of your research you should not proceed too fast. Take your time, read carefully through the information offered, ask yourself each time whether description and information are really relevant for your dissertation and do really meet your expectations. Make use of all information available on publications and research projects of the professors and try to “profile” them as narrowly as possible.
Repeat the process if not successful. If you were lucky and found someone whom you would like to become your academic advisor, write an e-mail. The first e-mail should not be too long. It is sufficient to introduce yourself briefly (name, university you come from, disciplines you studied), then characterize your dissertation project in one or two sentences and make this characterization the reason why you are addressing this professor in particular. With the last sentence of your e-mail ask for a time slot in his or her regular office hours. It is highly recommended not to attach a comprehensive CV and lengthy descriptions of your project to the very first e-mail. If the professor is interested, he or she will ask you to send further information anyway.
In case you are not convinced that your internet tour has been successful and you are still lacking information to be able to find an academic advisor in your field of interest, the only way to reach your goal is personal advice. Due to the vast field of scientific research in general, due to the large number of disciplines and professors of Freie Universität, there is no central helpdesk that could help you with your problem. Nevertheless, you can call the institute office(s) you put on your may-be list during your web search. Please do not expect immediate relief! Only in rare cases the office manager will be able to answer your questions directly. But if you describe your project as precisely as possible (and keep the description nevertheless short) and ask him or her whether he or she knows whom to speak to, you will almost certain be provided with a contact. From the person recommended by the office manager you will at least learn whom to ask and whom to address next, since this person knows his or her colleagues well and will be able to judge your project with respect to the scientific expertise it demands.
Since you now finally know which professor to contact, write an e-mail … This time you may well refer to the advisor you spoke to if you feel the need to motivate and justify your choice.