You need the pro version. See also
https://docs.kurviger.de/start?id=app/getting_started
Web and App are independent, so you can buy the pro app and stay with free web.
Hint:
There is currently a new version of the app in beta testing, which costs 9.99€/year.
New features will be only available with Kurviger2
If you want, you can register to the beta program and start right away with the new version.