My gosh they are changing so much from the novel and it's honestly pretty surprising.
I haven't gotten super far into the original, but the restaurant robbery was supposed to be 3 chapters long with even the back story of them. They were from Deadran as well and were under a criminal organization there. They had the Duke's wife held hostage at the restaurant as ransom and the dragons were fricking with them. Rurin was drunk the entire time while Serena trolled them. El spoke with Diean at the barn about the Deadran situation but not the poison. Serena kept trolling the robbers until they made it into the lair and scared the hell out of them. Ell punished Rurin with cleaning the restaurant and Serena by making her hold her arms outside of the restaurant. That's about what I read about it.