Hey @Dominik!
Thanks for reaching out.
But is there also an easy way, to stylize the userinterface for the “Edit Event” page?
There unfortunately is no such way to style the back-end of the plugin. 🙁 The plugin doesn’t really have its own “back-end”, it is just using the WordPress Core admin, so you would have to write extensive CSS to modify the back-end admin views.
You can see folks discussing how to do this in forum questions like this one: http://wordpress.stackexchange.com/questions/110895/adding-custom-stylesheet-to-wp-admin
And you can then piece together custom styles from there.
We unfortunately cannot help with writing customizations, but I would recommend checking out a [free!] tool like Firebug if you use FireFox, or the Developer Tools for either Safari or Chrome. They have “Inspector” tools that let you zoom right over the element that you want to remove or modify and you can spot the CSS from there.
Best of luck with your tinkering and customizing!
Sincerely,
George