Sometimes restoring from an old backup, especially a backup of a different device like an i Pad, can be less than ideal.
Between them, they're rated for 10 to 12 hours of battery life while browsing the web, checking email, and chatting.
You can fast charge but doing so creates more heat and can reduce the long-term health of your battery.
It's fine to amp up the charge if you need to refill fast and get on with your day.
But if you have the time take the time and let it charge at a normal speed.
Every once and a while, you get a problem you just can't solve. If you have Apple Care or Apple Care , you should absolutely book a Genius Bar appointment and avail yourself of it.
Rebooting, restarting, or resetting is the oldest cliche in troubleshooting. Sometimes a good reset is all that's needed to kick bad bits loose.