Hello and welcome to hcm forum,
Halitosis is bad odour which is usually caused due to plaque and calculus deposition on your teeth.
This plaque deposition can cause gingivitis
which can progress into periodontal infection
Please do get a thorough deep scaling done by your dentist
to remove the subgingival plaque and calculus deposited.
Use soft interdental toothbrush and clean your teeth in back-forth and up-down motion.
mouthrinse to gargle.
Rinse your mouth after every meals.
Hope this helps.