OpenSubtitles: The largest database. Search for "Dark S01" to find season-specific files. Subscene: Known for high-quality, user-rated translations.
If you are watching on Netflix , subtitles are built directly into the player. Dark (2017) subtitles
If you have your own video files (e.g., MKV or MP4), you can download "SRT" subtitle files from reputable community databases: OpenSubtitles: The largest database
If the subtitles don't match the timing of the voices, follow these steps: MKV or MP4)