International experience is an important part of academic qualification and personal development. It enhances your chances on the job market both within and outside of academia and research. Some academic funding institutions desire or even require knowledge of a foreign academic culture.
You can only profit from a stay abroad - be it for research, for a summer school, or for a workshop.
Your first contact for going abroad while pursuing doctoral work at the University of Oldenburg is your supervisor. With him or her you can discuss the host institution for your stay abroad, the timing and duration of your stay, potential sources of funding, and the supervision at the host institution.