The following Joomla components are important for creating online registration systems for local sports and fitness courses in Kölln-Reisiek:
1. **Community Builder or JomSocial**: These components allow the creation of user profiles and community features, which can be useful for managing members and their interactions.
2. **VirtueMart or HikaShop**: These e-commerce extensions can be used to handle course bookings and payments.
3. **RSForm!Pro or Fabrik**: These components allow the creation of individual registration forms and can be adapted to specific requirements.
4. **OSE Membership or Membership Pro**: These extensions are suitable for managing memberships and subscriptions.
5. **JEvents or RSEvents!Pro**: These calendar and event management components are helpful for planning and displaying courses and events.
6. **AcyMailing**: This component can be used for email marketing and notifications to course participants.
Conclusion: The combination of community management, e-commerce, form creation, membership management, event management and email marketing components forms a solid basis for an online registration system for sports and fitness courses in Joomla.