So to update all of you, I finished the setup with MIGX (really great tool) and the whole table is now build with it. So the page is loading way quicker now. What I find though is that whenever I change something and visit the page afterwards it takes forever again. As far as I observed this, it only happens to me as long as I'm still logged into the manager. If the page is loaded once after updating I can refresh (with cleared chache before) and the page is there immediately. I tried from another Laptop and the page was loaded instantly as well. So only first load with active login after changing something is bad...
Just to verify, how is the page loading for you?
http://bodhi-esslingen.de/yoga-kurse-esslingen-kursplan-bodhi.html
Further I fixed the "headings in paragraph" issue.
I noticed as well that the starting page and subpages are way slower. Maybe there is some more advice for me?
As Andy Tough requested here also a screenshot of my current cache settings:
http://bodhi-esslingen.de/images/screenshot-2.png