Visa
Detailed information about the visa and entry regulations for Germany, as well as an overview of all German embassies and consulates can be found on the website of the Federal Foreign Office.
If you have ever been to the EU, please have a look at the Short-stay Visa Calculator from the European Commission. It calculates the length of period you are allowed to enter the EU during your internship. More detailed information regarding this topic are also at the homepage from the European Commission.