[AC Question]

While I am charging my phone i am unable to use my phone because the battery depletes. But when i let it charge it takes up to 16 hours to charge.

[Sam_Gs7]

This Tech article may help to correct. The slow Phone charging process
Link: 10 reasons why your Android battery is charging slowly and how to fix them

[Rukbat]

The charger supplies a fixed amount of current. If the phone uses more than that amount, using it while it's charging results in a net discharge. (If you regularly discharge the battery past 40%, you'll kill it quickly - the more often you do it, and the deeper you discharge it, the faster it dies. Lithium batteries are not deep-discharge devices, they're lightweight devices. You don't want to be carrying a lead-acid battery around with you even though it can take constant deep-discharging.) You may need a new battery.