Yellow tooth implies deposits, you might need a professional cleaning.
Black spots on gums , this might be normal pigmentation or might be due to smoking ( if you smoke). It should be noted only when there is irritation or pain or presence of ulcer.
Single tooth mobility shows it is infected badly by caries and there is perapical abscess. It can be treated by RCT or extraction whichever needed depending on IOPA xray.
Bleeding gums shows, gingivitis. Please use soft brush and follow the correct brushing technique. Brush twice daily and clean your tongue every day.
Use salt water gargle or mouthwashes for 1 week following the professional cleaning.
Next Steps
Visit the Dentist and confirm the condition mentioned above and undergo the treatment plan accordingly.
Health Tips
Maintain good hygiene to save other teeth. Visit dentist every six months.
Hope this helps you.