Alex,
Sorry you're running into issues with Google and Twitter authentication.
For Twitter, the error you're receiving is because you haven't specified a Callback URL in your Twitter Application. That URL should just be your domain name/callback, like "
www.dackelclub.de/callback". That should get you past that error, and hopefully make Twitter work as expected for you.
I'm honestly not sure why Google is throwing that message. I'd recommend fixing Twitter to see if it has a similar issue getting your user information. That will help us narrow down where the problem is, depending on whether it's an issue that affects one, or both, social networks.
As for other benefits, JFBConnect allows for a more customized registration flow, including pulling data from each social network into the user's EasySocial profile. Beyond just EasySocial integration, we have Open Graph Actions, which let you post to a user's Timeline when they interact with your site (uploading photos, leaving reviews, voting for content, etc), Facebook invitations/requests, Open Graph tags for lots of different types of extensions, social sharing buttons and more.
I hope that helps get you started, but we'll figure everything out and get you going soon!
Thanks,
Alex