To export the calendar, go to Veranstaltungs- & Prüfungstermine and click on Meine Termine.
Now you can open up the developer tools and paste the script in AppointmensExporterGoogle.js into the console. It should download a CSV that you can import into Google Calendar.
There is also an exporter for Outlook calendar AppointmensExporterOutlook.js. You may have to change some values for reminder, privacy or category.