If your teeth are severely rotted then there's no way to save those rotted teeth.
If you have some rot which has created a cavity in your teeth then those teeth can usually be saved and fixed by cleaning your teeth and by installing a dental filling to that teeth.
But if you don't take care of your teeth those teeth can continue to rot out around your dental filling and rotted teeth can lead to gum disease and other dental diseases.
Rotted teeth and toothaches can lead to heart attacks as well as the tooth infection can lead to blood infections which can kill you.
So take rotted teeth seriously and see a dentist if possible about the rotted teeth and get those rotted teeth removed before they cause any other health issues.