Bad smell is coming from my mouth IDK what's the reason please help get rid of this 1. And I have dead tooth also is it creating this 1?

Bad breathe can be due to grossly infected tooth, it can also be due to plaque and calculus. Get your infected tooth removed and go for full mouth scaling.

Decayed tooth can also cause bad breath. Other reasons like dry mouth, tooth or throat infection, unclean tongue etc can cause bad breath. I suggest you to get the treatment for the decayed teeth, drink enough water to keep yourself hydrated, do tongue cleaning along with tooth brushing regularly.

Bad breath can be reduced or prevented if you: - practice good oral hygiene. - brush twice a day with fluoride toothpaste to remove food debris and plaque. - don't forget to brush the tongue, too. - replace your toothbrush every 2 to 3 months or after an illness. - use floss or an interdental cleaner to remove food particles and plaque between teeth once a day. - see your dentist regularly -- at least twice a year. He or she will conduct an oral exam and professional teeth cleaning and will be able to detect and treat periodontal disease, dry mouth, or other problems that may be the cause of bad mouth odor. - drink lots of water. This will keep your mouth moist. - chewing gum (preferably sugarless) stimulates the production of saliva, which helps wash away food particles and bacteria.