I am a native English-speaker, but regularly watch Netflix shows in other languages - just to practice my speaking skills in other languages.
The dubbing is good- in general. The problems the dubbers run into involve idioms, puns and other word games.
For example, in ST1, there is a scene where El walks out into the hall wearing her blonde wig and pink dress.
Mike, startled, says "You look good - - you look pretty good".
The translators have trouble capturing the subtle word game that is being played here. So, typically they capture the meaning but (in the process) lose the humor. In other languages, Mike typically says something like "you look good - you look acceptable."
