Calendar Single Page breaks font settings

Hi ??

The detail page of a calendar entry breaks the completely font setup of a client website :/

Check it here: https://www.gesund-und-punkt.de/terminkalender/

(For example entrys at Apr. 2017: https://www.gesund-und-punkt.de/events/walking-ohne-stoecke-57/)

What happens? ??

Thanks in advance for your support.