I have copied my site to a subdirectory for test purposes, everything works fine now. The only problem I have seen so far is the Media upload. When I try to upload a file I get a:
Unable to create directory wp-content/uploads/2016/05. Is its parent directory writable by the server?
The wp-content folder has a 755 permission, the uploads folder also.
I tried to add this to my wp-config
define( 'UPLOADS', 'wp-content/'.'uploads');
in the section before the table prefix is set, because I thought maybe I have to tell WP that the path changed
define( 'UPLOADS', 'unterverzeichnis/wp-content/'.'uploads');
but I get the same error.