Chosen Solution
I suspect my battery because sometimes even at 40 percentage the phone can just go off and immediately i get it plugged sometimes it can just show a high percentage charged like 20 percentage. Few hours ago i was using it and just went off at 20 percentage of battery and never came on again. i want to ask if i get a new battery can i fix it myself.
Yes, it sounds like a bad battery. You can follow the ifixit guide here iPhone 6 Plus Battery Replacement
As above or, check that your cable is actually charging. Sometimes the dust builds up inside the phone charging socket and and keeps the phone from charging, or check cable for broken wires.
