Visa information can be found on the website of the Federal Ministry for European and International Affairs: https://www.bmeia.gv.at/en/travel-stay/entry-and-residence-in-austria/entrance-and-residence/visa/
Yes, we organise two German courses for our exchange students every semester (for beginners and advanced). You also have the opportunity to obtain the internationally recognised ÖSD diploma (https://www.osd.at/).
Yes, there is the ÖJAB house in Eisenstadt, which is right next to the university. For more information and registration go to: ÖJAB-Haus Eisenstadt - Studierenden- & Jugendwohnheime - Studierende & Jugend - ÖJAB - Österreichische Jungarbeiterbewegung (oejab.at)
In Pinkafeld, you have the option of taking a room in the Pinkafeld guesthouse, which is a 5-minute walk from the university. For more information and registration go to: https://www.gh-burgenland.at/