Hey Nikolaus,
We unfortunately do not provide such specific code-level support for customizations. You’ll have to take the reins on finding where to make these customizations, but there are two resources that will help immensely in that endeavor:
First is the Themer’s Guide which you have already seen several times by now, but it is immensely helpful nonetheless → https://theeventscalendar.com/knowledgebase/themers-guide/
Next is a development tool in your browser that you can use to very quickly find out the elements you want to customize. These tools are all free! 🙂 Check them out: 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 you want to change; then just “search” in your plugin files for said element and you’ll know what to change and where to change it.
Best of luck with your customizations!
George