iPhone 7 slow network, battery drain, lightning port pro

I had a pretty unpleasant ownership with my iPhone 7 running iOS 11.1.2I got it when iPhone 7 launch, my friend got his about 1 or 2 month later and we noticed that my battery capacity is lower than his.

And few months after i got my phone, some little shiny dot unlike the matte black finish start to appear around the camerahere's the problem happened recently :1. Slow network speed, me and my friend had different carriers so I don’t know is cellular is slow too, but at home my laptop is able to get 90MB/s download and my iPhone 7 only able to hit 10MB/s.2. wired battery drain, so I charge to 99% and “opened low power mode” and when to sleep 6 hours later there’s only 39% remaining.(the battery app I found shows I still had 1700mAh capacity)3. my phone seems can't charge with factory cable(not even react anything), I tested with 2 phone, 2 adapters, 3 cable(2 factory 1 Moshi)