Hi @erikahonecker welcome to the /e/ forum.
When you have a regular /e/ install and you factory reset, the device does not reset to “how it emerged from the factory”, it mostly deletes the data partition, erasing (as you had imagined) all old user apps and settings and data. Leaving /e/ in the state it was the day it was installed, and before you had run the first start wizard. So the first thing you see after a factory reset should be the
bouncing e on a black screen.
So what state is the phone currently in … I cannot see straight off. A factory reset does undo Developer options.
Does the phone boot into Download mode and Recovery mode correctly? Does the Odin mode reveal any clues?