To answer your questions:
1) I don't know what do you mean with this. Real Time doesn't cooperate with other mods to create events.
2) It is not implemented and currently not planned.
3) Yes, this mod seems to be compatible with Real Time.

For the first question, like in rush hour, there were mods(assets) that allowed for custom events and the like.

You can use any asset that provides the Rush Hour custom events. The events will then take place in those buildings. However, you won't have that event controls of Rush Hour. There will be no impact on the economy too. This is because the Rush Hour events are partly supported.

i tried to add a Random Event XML-File for this asset: https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=790423541
the XML-File is created after this guide:
https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=630448832
i also added a second xml-file under the events directory in th rela time/event directory, but no event is starting in this asset.
is this only possible for some special building category or is there another problem?

You don't need the additional XML file in the Events directory of Real Time. Those events are pre-configured for the vanilla unique buildings.

You only need a custom XML file in the asset's directory as described in the guide. However, not all information form those XML files will be used by Real Time - only the ChanceOfAttendingPercentage section will be used.

Note that the BuildingName attribute must exactly match the building name in the asset editor. Otherwise, the event won't happen.

Furthermore, the events are scheduled randomly. You might have to wait for a game week or even more for an event in a particular building.

OK, thanks for the answer, I will try to wait for longer time for the event to appear. The name is the same and time since the building is built is now about one week in game. So what should be the longest in game time for the event to appear?