Jade plant rotting?

Your plant is likely suffering from cold or over-watering or both. Tip out your plant and check the roots. If you get to it early enough you can simply remove the mushy roots, repot in drier, more airy compost, raise the temperature and your plant may pull through.

If it's too late then cuttings are your last chance. But again, improve your compost/temperature to avoid a repeat.

Thank you MW. What kind of temps does it need, he keeps this in his room, maybe it is the soil, cause it has rotted roots but not ends of the branches. So I should try to root cuttings? Does it require any special treatment to root? In soil or in water?