The distances in Regensburg are usually short and many of them can be done on foot. Taxis, eScooters (Lime, Superpedestrian, TIER, Yoio and ZEUS, note specific parking regulations in the world heritage zone of the old town: https://www.regensburg.de/leben/verkehr-u-mobilitaet/elektromobilitaet/e-roller-e-scooter) and hire bikes (TIER, https://donau-donkeys.de/) are of course also available.
Nevertheless, the bus of the Regensburg Transport Services (RVV) is usually the means of transport of choice for the route between the hotel and campus, for example. All tickets can be purchased directly on the bus. Alternatively, the RVV app can be used as a digital solution: https://www.rvv.de/handy-ticket.
You can find a quick overview of the relevant bus connections here in the section of the bus map.
Bus Map