Proton Calendar on iOS being painfully slow

It is not often i ask questions here anymore. But I am generally interested are there people who use the Proton Calendar app on iOS? I tried to set it up for some relative but while the Android app is already slow the iOS for proton calendar seems to be unusable. Maybe it is because they have quite a busy schedule but i hope that should no the reason. If you navigate back a couple years, the app seems to crash. Ended up with setting it up as web app for now, which seems to be a lot faster, and actually does offer search, while the app does not… Are there people actually using the iOS app? Am I doing something wrong?