2006 Ford Focus Engine light maybe O2 sensor

My 2006 Ford Forcus is not working properly. The engine light is on and when I stop the car it will sometimes stop if idle for awhile. I have to sometimes ease into the stop so it will not go dead. It even goes dead if I when slowing down for a turn. Which sometimes becomes an issue if turning into oncoming traffic. Just recently the car came to one of its, now regular stops, and wouldn't crank back up like normal. And it was also smelling like burnt rubber. When it finally did crank up. I couldn't step the gas to get it moving. Luckily I was on a hill so it just coasted to a complete stop.