Please note that Germersheim is located about 110 km away from Mainz in the vicinity of Mannheim and Karlsruhe.
The airport Frankfurt(Main) is the closest main hub within 1.5 to 2 hours by train, with one change of trains in Mannheim. Stuttgart airport, too, is within train distance of about 2 hours.
Trains to Germersheim run from Mannheim and Karlsruhe Hauptbahnhof (Hauptbahnhof = main station). There are two train stations in Germersheim: "Germersheim" and "Germersheim-Mitte/Rhein", the former being the main station somewhat outside town, the latter being a smaller station close to the town centre and the institute, but only being served by about every other train.
Train travel information for Germany can be found (in English) under