I just noticed something on my car that makes me wonder if my engine has a problem. Before 1 month I broke my exhaust when trying to take a turn when the car hit the pavement. My exhaust makes my car dirty... but that is not the problem... I noticed that around the flywheel there is a brown spot which I cannot distinguish if its coming from my engine or my exhaust....

a pic of it...

Your engines front bearing will slightly leak out oil, it is impossible for it to be completely sealed. Once your engine is worn out it will leak out more and more. It is normal for the front bearing to leak out abit of oil. I think this maybe what your talking about. The oil goes out the front bearings and gets on the flywheel sometimes and spreads it on the chassis plate