iPhone 6 discharging instead of charging
If you have a Mac compter you can use you can connect iphone to the comuter and use coconut battery. This Mac app will give you information about your battery. Best to have your phone fully charged if you can do that. It will work though without that constraint. I used it and it showed me that even though phone was fully charged it only had about 50% charge stored. My battery was dying.

Based on your graphics though it appears your cable or charger is not adequate for your phone. I'd check the battery first. If battery is ok, you might try a different cable and see how that works.