Our school runs a Wordpress theme we purchased in 2013 (Cleanspace Business, author mad_dog).
It always worked out great so far but with the latest WordPress update (5.6) the theme doesn’t have the white site background but a transparent scrolling site (I don’t know how to express it better).
The address is http://www.augustinianum.de
Who can help fix the problem and restore the original page layout?
My advice is to put some better template which supports new versions off WP and have regular updates. Also your SSL certificate is not setup good. Half sites is http and other https.