After procrastinating for months, nowadays I eventually had no excuses anymore for not finishing the app my father asked me to do after releasing his latest book "Veranstaltungen 4.0". Basically the app contains the same contents as the book and makes them filterable by e.g. amount of participants or participation grade.
You can buy it now in the app store for 7,99€: https://apps.apple.com/de/app/veranstaltungsformate-event/id1502391028?l=de&ls=1
App development is no fun at all. Like XCode comes up with new random issues after each update. And you need to update and re-compile all external libaries everytime Apple decides to push a new version of Swift, which sounds easier than it is.
So don't expect any further iOS native apps from me soon as working on it made me realize once again why I chose to focus on web development.