i am confused about the exit system, can i only have one exit per room.
You can have multiple exits. I think I know where the confusion is coming from : Bitsy HD is not updated to the newest version of Bitsy, where exits were overhauled. So the exits in HD work in the "old way". If you check some older bitsy tutorials or ask around on Bitsy Discord, I am sure you can find how to add multiple exists per screen.