If you are using a sitemap you have to break the time up into hours and minutes (and seconds) and manage each individually with separate setpoints. Use changes to those Items to consolidate them into a DateTime Item in a rule.
In MainUI, just use a standard oh-input-card with “type” property set to “datetime-local” and you will get a nice date time picker. Or install and use DateTime Standalone Widget. If all you want is the time, I think you’d just use “time-local” or “time” as the “type”. Make this widget update a DateTime Item.
Finally, use the Time is <item> rule trigger for the “Szenenausewahl” rule where <item> becomes the DateTime Item (you don’t need the Aufstehen rule at all).