thanks for answering. I do have both firebug and web developer tools installed.
This here is the jevent calendar with the css file: http://www.joomlaos.de/images/stories/images5/jevnetsmcalf.png
And this here is the K2 calendar with the css file: http://docs.joomshaper.com/images/templates/travel/2_4_0.jpg
Just overwriting the jevent css does not work of course and I’m quite new to the whole web developing business so any tip or suggestions would help out a lot.