Ok, thanks. Now Movies works, but my series are not shown under TV Series.
Have changed content to TV Series (only 1 season) and added it to the library after changing the titles to e.g. "In the beginning_ep01.mp4", but afterwards there still is the option to add to the library...
Within the Videos folder, where I added all Media sources, you can of course just open the series folder and play it that way, but its a bit cumbersome. I linked the whole source folder to Movies and then subfolders to TV Series and others.