Please see nearest dentist for clinical assessment , doctor will tell you which tooth can be restored, which need x ray. For that you  need check up. And for bad smell also there are various reasons. Poor oral hygiene Liver and kidney disorders Gastrointestinal disorders Diabetes Certain food items like garlic , onion.

Hi sir...     Your teeth probably got cavity     First and foremost is to take XRAY (IOPA) to rule out the cause     Dentist will according plan that teeth needs a filling or whether it can go for an root canal treatment   If the cavity reaches the nerve layer(pulp layer) root canal treatment should be done If not then filling can be done    Bad breath is due to hard and soft deposits inside the oral cavity, There are several causes are * vit deficiency, Iron deficiency anaemia *accumulation of food deposits (plaque ,calculus, stains) *gastric ulcers etc It should be cleaned by dentist by a procedure called scaling and polishing (teeth cleaning),it is mandatory to do scaling every 6months

Hello Visit the dentist and a x ray done if filling is required get it done

You probably have tooth decay and require fillings. Consult a dentist near you and they can do the needful