As a project assistant, you will work an average of four years on the execution of a project in preparation to your PhD thesis. You will be involved minimally in other tasks such as teaching assignments or rendering services. In this case, you apply for a vacancy, which indicates that your PhD subject will be determined in advance and be part of the broader framework of the project in which you will be involved.
As a PhD candidate, you can always apply for vacancies for assistants, so check our vacancies page regularly. It does not necessarily mean that you have to have excellent degrees in order to be considered for a job as a project assistant: everything depends on the quality of your co-applicants. Of course, you have to be extremely motivated to carry out research.