BuddyPress.org

First of all, please do not cross post. Your issue will be addressed in time.

Secondly, did you search the forums before posting? This issue has been addressed several times in the past. It is an issue with 1and1 and how they set up hosting. It is not a BuddyPress-specific issue.

https://buddypress.org/forums/topic/error-500-internal-server-error-an-internal-server-error-has-occured-please#post-23821

https://buddypress.org/forums/topic/500-error-after-uploading-buddypress-102#post-18421