I have a heavy fuel smell in the cabin of the car. Just bought 2008 A5. Smell started the next day, after I filled the tank.

Hey how are you. I’m not sure how this works but I have a question for a mechanic and I’m not one myself I know how to work on cars but long story short. My girlfriend woke me up this morning stating her car smelled like it was burning apon starting she let it sit for a little bit and the smell somewhat got worse. I’m thinking it’s an exhaust problem because how else would we be smelling it if there’s no fire nor smoke arising besides coming from the exhaust but I truly don’t know what do I need to do and where do I need to start with looking. I would take it somewhere but I don’t know if it’s drivable. Thank you! Also like to add it’s not much of a rubbery smell more like a straight out fire smell maybe the belt? Once again I have no idea where to start 😅 Thank you !