when i start my chrysler 2007,why is a cloudy of white smoke,smells like sulfix on 2007 Chrysler Sebring

the 02 sensor been replace,an the is still a cloudy of white type smoke coming from tail pipe,smells like sulfix..what can it how to repair

Check your coolant level to see if it is low. Sounds like a possible head gasket leak and you are burning antifreeze. This is the white smoke you are seeing.
what can i there an sealer or do i need to rplace the gasket
You can try a sealer but, they usually work only for a short while. Gasket will need replaced for a long term solution.
what is an misfire..po 300
That is a multiple misfire code. The engine is misfiring due to increasing levels of coolant getting through the head gasket and disrupting proper ignition of the fuel/air mix. You need to go to a shop and get a diagnosis and estimate.