Thanks a lot for fast reply, but I cannot check it anymore, because:
My solution or simple workaroud was to move physical the complete wordpress installation from sub to root directory. Now Nextgen gallery works well, upload, etc.
Best regards
Gerwin
It seems to be a similar problem as https://ww.wp.xz.cn/support/topic/nextgen-problem-since-moving-site-from-subdirectory?replies=3
Links are working, but no upload to a new gallery is possible…
