Hi there, Matthias! Thanks for getting in touch and welcome to the forums. 🙂
It sounds like you’re using the Default Events Template, which is great! You can override this and set up your own copy within your theme (see our Themer’s Guide for details) so it would live at:
[your_theme]/tribe-events/default-template.php
You would then customize this to add a sidebar where you would like it. What works well for you and your theme is something you’ll probably need to discover through trial and error. At code-level adding the sidebar could be as simple as this, though:
get_sidebar();
Once you’re happy with this you will want to make sure it only displays on single event page. You just need an extra statement preceding your code to load the sidebar. Here’s an example:
if ( tribe_is_event_query() && is_singular() ) get_sidebar();
Does that make sense? Will that work for you? Please let me know.
Cheers!
Geoff