Thanks for asking the query,
T he black colour areas which you are having can be developmental areas of hyperpigmentation
so you not need to worry at all.
Can be a fungal infection
Visit to the Dentist
get the chekup done, biopsy of the lesion can be helpful.
Maintain a good oral hygiene
, clean the tongue with a tongue scraper or a soft bristle toothbrush.
Take multivitamin suplements and folic acid.
Take complete balanced diet, drink lots of water and keep yourself hydrated.
Hope this helps out.