The "Full Calendar" is not much of a calendar. It can show data from a calendar-file that's it.

And each time you have changes to the calendar you have to export from the source edit your project to link to the new data and then upload the project - unless you make a routine that can upload and replace the data-file.

If you want a free calendar that is 10.000 times better take a look at the LuxCal calendar.

https://www.luxsoft.eu/

Also see these posts:

https://helpcenter.websitex5.com/de/post/173883

https://helpcenter.websitex5.com/de/post/198334