Whether you need a visa or not to enter the Netherlands can be found on the website of the Netherlands Organization for International Cooperation in Higher Education (NUFFIC).
If you are a citizen of Australia, Austria, Belgium, Bulgaria, Canada, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Japan, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Monaco, New Zealand, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, the United Kingdom, the United States of America, or the Vatican City State, you do not need a visa to enter the Netherlands, neither for a short, nor for a long stay. All you need is a valid passport.
As a citizen of a Schengen country you may travel through all Schengen countries freely.
When a visa is required, you must arrange it yourself.
To obtain an entry visa (in Dutch: Machtiging tot Voorlopig Verblijf: MVV) you must apply to the Dutch Embassy or Consulate in your home country.
You need to submit a letter stating that you qualify for admission to the Radboud University Nijmegen, or an admission notice issued by the Central Students’ Office (Dienst Studentenzaken). We do not know how long the visa application process will take. Experience shows that it may take from a few months to one year.
A guide to Dutch immigration laws for Non-Dutch nationals is also available on the NUFFIC homepage, including information on requirements for a residence permit, a work permit and a health insurance as well. Please read also the visa and residence information issued by the Radboud University.
Please ask the International Office of the University Duisburg-Essen regarding visa matters for Germany.