Because this is a GERMAN BluRay release, it typically runs at 23.976 fps . If you notice the text drifting away from the speech, ensure your player isn't forcing a different frame rate.
The .srt format is the most widely compatible. If your file is in .ass (Advanced Substation Alpha), it may include custom styling that some older smart TVs cannot display properly. How to Use subtitle Undine.2020.GERMAN.1080p.BluRay.x265-V...
Keep both the video and the subtitle file in the same folder. Because this is a GERMAN BluRay release, it