The file extension .mkv.mkv suggests a naming error; you can safely rename the file to end in just a single .mkv to avoid playback issues.
: If the video has no subtitles, you can find the matching text file on major subtitle databases. Search for "Chainsaw Man S01E01" on: OpenSubtitles.org Subscene.com A4kSubtitles (if using Kodi) Chainsaw Man S01E01 HD | STAGATV.COM.mkv.mkv
In certain online communities or when using specific translation tools, users refer to the external text file that provides the dialogue as the "paper" for the video. How to get the "paper" (subtitles) for this file: The file extension