A detailed description of every SINGLE scene from the trailer, what we know and what we don't (with timestamps)
Here's the trailer for those of you who did not watch it: https://www.youtube.com/watch?v=cq2iTHoLrt0
[ 0:00 - 0:10 ] Just the ending of the last season, nothing particularly new here.
[ 0:00 - 0:19 ] So, here we get the confirmation that we'll get to know where Jonas truly came from. As the current timelines are all stuck in a "knot" (repeating cycle). We know from H.G. Tannhaus, that once an artifact went back to the past from the future, its true origin becomes unknown. In this trailer, it seems like we'll learn what was before the knot and where it all started. Also, here we see a scene with the Stranger (Jonas) with his hair cut looking at a paper with his name. He is holding the piece of paper that he got from younger Noah (he said it's from Martha) before the apocalypse in the last episode of season 2.(I initially missed this, thanks to u/abyssiphus and u/testreddit01LP for pointing out).
[ 0:20 - 0:24 ] This one is big. We get to see a wall that seems to represent the beginning of the knot, which apparently has 2 directions. It's likely this is where 2 separate dimensions started. This scene is perfectly cut so we don't see who one of the parents of Hanno Tauber (Noah) and Agnes Nielsen is. Also, this might have been exactly what the show was trying to tell in Season 1 Episode 4 when Magnus entered in Franziska's class and the teacher said: "Symmetry is a special kind of doubling. The repetition is mirrored along a central axis. So, the repetition begins at an imaginary point and branches off in two opposing directions. There are several encrypted references to later events in the novel". At this point, I think we all know this was a sneaky spoiler lol.
[ 0:23 - 0:27 ] Martha said: "The beginning for everything. In your world. And in mine.", referring exactly the kind of symmetry the teacher was talking about. It's pretty clear now that we'll get to know the origin of everything and how the knot started.
[ 0:27 - 0:30 ] Martha teleported in another dimension. We know this because the device created a yellowish/orangeish sphere, unlike the black one that appears when you teleport to another timeline. Also, if you pause the last episode of season 2 on Netflix at around 54:08 when the explosion reaches the house, you're going to see the exact same orange color inside the house, before Martha and Jonas teleport away.
[ 0:30 - 0:33 ] Martha said "Today is the day everything began.", the scene illustrating what seems to be the same forest Jonas was in when he was stuck in the future. I'm not entirely sure when this "today" is referring to, but probably right after the apocalypse.
[ 0:34 - 0:37 ] Again, somehow illustrating the symmetry between the two worlds.
[ 0:37 - 0:40 ] Martha: "form a knot that is intertwined" - this might very well mean that the dimensions affect each other as well, just like the timelines do. There is also a scene showing Elizabeth in what seems to be the post-apocalypse, meaning she survived in the bunker OR in what could also be the past, so she could become Charlotte's mother. The background is quite blurred, so we can't know for sure whether it's a scene from the past or the future.
[ 0:40 - 0:43 ] I'm 99.9% sure this is the Adam version of Martha, possibly called Eve. I initially thought this might be Claudia Tiedemann because we were told she is in some way fighting against Adam. But the hands don't seem to look like hers and in a future scene we see this person is a little taller and skinnier.We're also seeing her separating a book and I believe the clock that Elizabeth was holding in the previous scene, revealing what seems to be a notebook or something similar containing papers. There is also this new character that seems to be with all versions of himself in EVERY SINGLE SCENE he appears. We haven't seen more than 2 versions of a single character being together so far, so this is something new. Also, now this Adam version of Martha (Eve) is the one talking (I believe), saying: "Everything repeats itself".
[ 0:43 - 0:46 ] Here we see different versions of the same people. It might be that they are from the same dimension, but different timelines or it might be that they are from different dimensions. First, we see Katharina (and we know she didn't travel in time in the previous season, she might do it now, or she might just be shown from 2 different worlds), then we see Elizabeth (first seems to be the one in the future, and the other one seems to be in the past, just like Katharina, it might be that we see her in 2 different dimensions) and then we see Ulrich (either from 2 different timelines, or 2 different dimensions). When I look at Ulrich and Katharina, I tend to believe that they are from different dimensions, but when I look at Elizabeth I tend to believe it's just 2 different timelines. Maybe it's just me.
[ 0:46 - 0:48 ] Martha dying, nothing important here.
[ 0:48 - 0:49 ] This is also BIG. So this is for sure the past, and if you pause the trailer, you can see that there is a woman (who looks like Agnes Nielsen because she's kind of elegant, and she tends to wear dresses like the one in that scene, it might as well be Martha or someone else). We also see 3 boys/men right in front of her (I believe they are that mysterious character that is always with himself from all 3 timelines, I might be wrong though because the scene seems to illustrate the creation of the time machine) and there is one more guy on the left (I have no idea who he is, maybe Noah?). This scene seems to illustrate either the creation or just the activation of the time machine using the god particle.
Edit: Actually, it looks more like the person in the middle is a girl, it might be that the 3 people are actually Bartosz, Franziska and Magnus. The girl might be Martha also.
[ 0:49 - 0:50 ] This is Elizabeth and some other person (I can't tell who it is) in what seems to be the future Jonas was stuck in. It might be just me, but it looks like Elizabeth's face is not as destroyed as it was when Jonas was in the future, she's missing some scars. They are walking towards the god particle, likely the one Jonas used to leave (or will use to leave).
Edit: u/Gregxus said that the other person here is Charlotte, and this seems to be true.
[ 0:51 - 0:52 ] Again, this mysterious character, with his other selves, playing with the god particle.
[ 0:52 - 0:54 ] The other dimension Martha walking with Jonas (?, might be someone else) in what seems to be the cave if Winden wouldn't exist. <- this is something Ulrich said when he was young, if I learned something from this show, is that EVERY single thing the characters say is there for a reason (see what I wrote above about the teacher).
[ 0:54 - 0:56 ] This scene is from the future. Not sure which dimension though. The character might be Jonas, but it doesn't seem like it, his mask is red this time, it was yellow before. <- I might be skeptic here
Edit: u/KhlavKhalash77 mentioned that it could be young Noah, and now that I look at it, it really lookes like him.
[ 1:01 - 1:02 ] This might also be BIG. When I saw this scene, I immediately thought could be the passage between 2 different worlds, just like the one from the cave was the passage between 3 different timelines. I'm sure there are a lot of secrets Adam hasn't revealed yet.
[ 1:02 - 1:03 ] Someone (?) dragging a body into a hole. It might be the equivalent of Mads Nielsen's body in the other world. The hole is not that deep, so the body is slightly visible (just the Mads was). However, the body is inside a bag, so what I said might not be true. It could obviously be taken out of the bag before being burrowed, but idk. This could also be the survivors just borrowing the bodies in graves. Remember when Jonas went to the future, there were a lot of graves of all the people who did not survive.
[ 1:03 - 1:05 ] Images with some of those bodies in what seems to be the same kind of bags. Petter Doppler is also a survivor because he was in the bunker, but we kinda knew that.
[ 1:05 - 1:14 ] They are talking about a single world, not two, without YOU <- which could mean Jonas in his world and Martha in hers. At the end of the scene, we see what seems to be the destruction of the god particle, and possibly of all the portals everywhere. This would unknot the knot, possibly making Jonas (and Martha?) disappear so that a normal world could exist.
[ 1:16 - 1:20 ] Again this character, burning (possibly) the equivalent room of Adam, in Martha's world. A lot of papers seem to be on the ground, those might be the ones from Adam/Noah notebook (including the "missing" ones).
[ 1:22 - 1:26 ] The same action done in different worlds by different people. The first one seems to be Katharina killing someone (very likely an adult). The second one is trying to kill a child (just like Ulrich did) and the third one is Ulrich trying to kill Helge. It's a little strange because there are 3 actions of killing someone like that instead of two. You would think there would be Ulrich killing a child and Katharina killing a child, so that the worlds could be perfectly mirrored. However, there is Ulrich killing a child, Katharina killing an adult, and someone (who would be very strange not to be Katharina, but it doesn't really look like her) killing another child (the equivalent of Helge (who we don't actually know who it is, it hasn't been revealed anywhere so far).
Edit: u/Gregxus said that the first person is Elizabeth killing someone. I'm not entirely sure about this thing, because we've never seen Elizabeth middle-aged, only old and young. (he added a proof: https://i.imgur.com/38D4Pow.png)
Also, he linked this post and it looks like Katharina is killed by her own mother.
[ 1:28 - 1:32 ] Martha and Jonas leaving the cave that seems to be in another world without Winden and someone approaching them. It could also be that they went to the beginning, when it all started (although it would be a little weird that there is no vegetation if it's the same place years before). I really think it's a world without Winden, given the fact there was a hint about this when young Ulrich talked to young Hannah in the bus station.
[ 1:32 - 1:34 ] Another meeting between Jonas and Adam, the circumstances are unknown.
[ 1:34 - 1:36 ] Noah seems to have gone through a lot. His face looks like he's a little sad and scared, it's not really the Noah face we are accustomed to. Maybe he realized Adam shouldn't be trusted, but it's too late. There is a little blur on the bottom right part of the screen, he seems to be talking to someone with long white/gray hair, possibly to Claudia Tiedemann or Martha's version of Adam (in which case we're not sure which Noah this is).
[ 1:40 - 1:42 ] I'm 95% sure this is Adam and Eve (Martha's version of Adam) pulling the lever at the same time. You can look in the trailer at 0:41 to compare the hands. I'm quite sure the hands from 0:41 and 1:40 right are the same; and the left one from 1:41 is Adam's hand. Also, he's the one who says "It is time", so there is a good chance it's him.
[ 1:43 ] Here we can see Charlotte Doppler and Aleksander Tiedemann in red hazmat costumes. This is probably the Apocalypse taking place in the other world.
Edit: u/ec-freak said that the other person is Tronte Nielsen, not Aleksander Tiedemann because of the beard. Honestly, I didn't notice the beard at first, but it does seem like it's there. I'm not entirely sure though.
[ 1:44 ] I honestly don't know what the heck is that.
[ 1:47 ] In one of the frames, we see that even though there is no Winden, there is still a bunker. Just like there is still a cave.
[ 1:50 - 1:57 ] Here we see Eve (Martha's version of Adam) staying in front of a painting with Adam and Eve, followed by that mysterious character that's always with his 2 other selves. She says "And thus the cycle repeats itself", which is actually very creepy. Imagine if the show would end and nothing would have changed, the cycle keeps repeating and there's no way of knowing what was before. This could be a possible ending.
Alright, so that was me staying 4 hours looking at the trailer and writing a post on reddit. If any of you comes with a great explanation of any of the scenes from the trailer, I'm editing the post accordingly.
Thanks for reading this!