Hey,
This COULD BE a condition where the taste buds overgrow and therefore causing the stains of tea,coffee,tobacco use to accumulate on them.
This condition often occurs when there is poor oral hygiene,eating soft diet with no roughage that would otherwise mechanically clean the tongue surface.
Burning sensation could be due to start of accumulation of bacteria on these overgrowths.
IN most cases, brushing your tongue with toothbrush or normal tongue scrapper would be sufficient. So start using a tongue scrapper daily, the blackness would go little by little. Also gargle with normal water after each cup of tea/coffee/colddrink.
But before that consult a dentist and make sure of the diagnosis.
Next Steps
Visit your dentist.
Health Tips
Add food with fibre like fruits in your diet.