Actually, dark is very complicated series but it is very interesting to watch if you love time travelling although you can watch the show with the help of family tree .  Here is the season 1 trailer .



overview
In the season 1, the children were start missing one by one in the town winden ,to find out those children their parents and their local police officer investigate different things and suspect different people from different angle . show gets complicated when they know there is something weird in the cave of the winden or there something mysterious secret underbasement of nuclear power plant which chairmen is alexander tiedemen , husband of regina tiedemen .
                                                          To know this show you cant understand reading you have to watch it from the first with no eye close ,so i can only share one people opinion on it .Have a look.

*WARNING: SPOILERS AHEAD. READ AT YOUR OWN RISK. I apologize for it being a long answer, but I have a little part of my brain that has been thinking of this answer since December 2017*
I personally was a bit intimidated by the both the name of the show and the fact that it was in German because although I had watched movies in German, I had never heard of any show in the language, especially on Netflix. As I watched the show the week it came out, I was a bit confused the first few episodes as they passed by slowly and once the fourth or fifth episode came about, that was when it became interesting.
The show is set in a quiet and dark (haha, no pun intended) town outside of Berlin called Winden, where it’s almost never sunny. The show depicts three different time periods of the town’s history and each of these time periods are somehow connected. The characters seem to have a connection with one another without knowing that they all have this connection and that they are all hiding something without knowing this. There is also a whole lot of time traveling and missing children and an evil force behind all this (sound familiar??), granted if you’re into that stuff. There's also a bit of romance, but of course it had to have a dark and shady twist to it.
The acting was well-done, albeit some of the characters were over-acted (Franziska is an unnecessary character). My personal favorites came from the performances of:
  1. Jordis Triebel as the wife of the police chief (played by Oliver Massuci)/principal of her kids’ school, Katharina Nielsen. As the season progresses, she becomes more involved and becomes more protective/open, especially after her child goes missing. I know how heartbreaking it must be for not only the fact that her child is missing, but also to find out that her husband is having an affair.
  2. Louis Hofmann’s performance as the confused and isolated young man whose father’s suicide triggered it all (the truth about Michael Kahnwald and who he really was), Jonas Kahnwald was stellar. I personally enjoyed watching him figure out the real secrets and cannot wait for what he has in store for season 2, especially after that last scene in the last episode. He's a new and rising talent to keep your eyes on and has been in some modern German movies. Every time I see a yellow raincoat and blue jeans, I always seem to imagine him in them.
  3. Oliver Massuci’s performance as the angry and revengeful (former) police chief was relatable and inspiring. As someone with younger siblings, I understand the worry he has for finding his missing child and taking as many risks just to find his child and solve this mystery, albeit they may be negative. I sympathized with him on this fact, which is why I consider him the anti-hero and the backbone of the show.
  4. Maja Schone’s performance as Jonas’ desperate and manipulative (to others) mother, Hannah Kahnwald. Damn, this woman did anything to get her way. I won’t say anymore, otherwise I will be writing the entire show. I can't believe how deceitful and manipulative someone could be until I watched her in Dark.
Ultimately, as the show’s first season came to an end (I was watching it during the Christmas break), I was happy to learn there was a second season coming out sometime in 2019. Here is a link for this: ‘Dark’ Season 2 First Look: Netlix’s Mind-Bending German Series Is Going to Get A Lot Bleaker. Overall, it was an interesting show with a mysterious nature with more plots being uncovered as the episodes pass, which basically means that there is a new revelation every episode as the main mystery has yet to be solved, which was something I liked. There's a bit of cursing and one of the downfalls may be the language barrier. There is a dubbed version of the show in English (for me as an American with little experience speaking German), but it is better in the original German with subtitles, which requires one’s undivided attention.
I understand where people are coming from with the comparison of this German show to its American counterpart, Stranger Things with the missing children and the 80s music/setting(s), but that’s pretty much the only things they have in common. For me, this show partly inspired me to learn German in college, but of course there were other reasons. Dark and Stranger Things each have different subplots and that’s what makes each of these shows unique. Overall, if you enjoy a thriller and some intensity, along with time travel and a shitload of betrayal and drama (and learning a new language), then Dark is the show for you. If not, then I would skip this show and probably watch something like The OA or Stranger Things, which have more clearer and straightforward plots.