Put each movie in its own folder and include the release year when different films share a title.

Movies/
  Arrival (2016)/
    Arrival (2016).mkv

Keep bonus material, alternate versions, and subtitles inside the movie folder with names that make their relationship clear. Do not place several unrelated movies in one folder if you expect per-movie extras or artwork.

Before rescanning

If you correct a name after Portico has already matched the item, scan the library again. Use the match tools on the detail page when the file is organized correctly but the selected title is still wrong.