Hey Heiko,
1. Hotspots is showing the event locations, not the events itself on the map. In the content - hotspots matukio plugin you have the option to map the matukio categories to hotspoits categories. So for example events in the disco category will land in the hotspots discos category and events in the "concerts in the park" category will land in the appropriate hotspots category.
2. Yes.
3. Yes, we have a simple event submission form
matukio.compojoom.com/submit-event
4. No, You can however use this
compojoom.com/support/documentation/hotspots/ch05#id428912
but it doesn't really make sense for 10 events on the map...
Cheers,
Daniel