The full capacity of battery dropped very much in 2 3 days

I brought dell g15 and after 5 months when i checked the battery report see what i found.

The battery full capacity was normal but in some days it almost fall 10000 mWh. I don't know it is normal or my laptop is havig any issue . I uses my laptop always on charging while playing games or anything , Is it ok to use laptop while charging. please help me regarding my issue.