Remember when he approached Tronte in the woods with the bracelet for his Mum but Tronte gave it to Jana not Claudia?
He is Agnes's previously unseen "abusive husband"
When Adam fried pregnant Martha in the ball he created the weird entity that exists simultaneously
Adam believes he must succeed by maintaining the status quo, and believes he will succeed by frying Martha, but nothing happens. In several timelines he then believes that he must kill Eve thats why she expects him, but he eventually realises this wont work either.
Eve's motive is in keeping their son alive
To further complicate Jonas' linear timeline begins in 1888 so by the 1920's "Stranger Jonas" has aged and has been burned so frequently, he has become the monster who believes that for him to succeed Martha must die. In fact neither realises they are just stuck in a time loop created by Tannhaus and it takes Claudia to figure this out. But she must get young Jonas to act because older Jonas is too warped.
Someone at some point (likely Noah) told 1950s Hannah, that she needed to help Jonas, and she used the suitcase to travel back to whatever year it is. Stranger Jonas now Adam recognises his sister as the girl his younger self met with Elisabeth in the apocalypse years, kills his mother, abandons his sister into the future, where she was raised by grieving Elisabeth, only to send her back to the past to seduce Bartosz and conceive Agnes and Noah.
Sija's parents are Hannah Kahnwald and Egon Tiedemann so Bartosz is his own great Grandfather