A Todo App with Caldav and countdown timer support?

I have horrible ADHD and need such a thing.

Many tasks have a countdown, and I would like to:

• on Android have a widget on the homescreen displaying the task and a countdown
• sync it witg DavX5 to my mail provider and then to Thunderbird
• easy interface, modern etc

Do you know the best app for that? Dont really want to try every app again, even though I did that (Simple Calendar is the best calendar!)

I am posting this here because the community is damn huge.

I tried ProgressBars and it is okay, but widget placement requires a new event (no no existing, weird workflow) and it doesnt support CalDav