Renewals are automatic by default and are taken care of by the Certify background service which runs all the time, even when the UI is not running etc. There are no scheduled tasks.
The Community Edition currently covers up to 10 managed certificates, each certificate can have up to 100 domains included.
By default error notifications will be sent to your contact email defined under Settings > Certificate Authorities > Accounts. The app will attempt renewal a few times before a notification email will be sent. Failed renewals are attempted is a ‘back-off’ approach, so first hourly, then every 2 hrs, 3 hrs etc, up to very 48 hrs. This is also included in the Community Edition currently.
Which page did you look at for most of your information when reading about the app? I’ll get that updated regarding automatic renewals.
Regarding the auto renewals: it’s explained online fine, but the app doesn’t mention it in the GUI clearly I guess I was in doubt to close the app, as I was wondering if and how the auto renewal would be active.