Iphone 5s, keep getting bogus battery readings on power level

I've had this phone maybe 5 ? Yrs now, 32 lifetime hrs, battery drains normally most of the time and then will inadvertently say it's really low like 12 or 9% or some dead % after a 2 minute internet on DU or FB or email jaunt...

so I plug it up and within minutes it says battery is charged at twice more the level it was before the activity.... I asked a coworker to witness this auto recharge to make sure I wasn't seeing something I wasn't seeing...

20% to 100% in 5 minutes?

tonite left work with 38% and drive home, plugged in phone at 3% and it slowly crawled to 23%... 20 mins? so I turn it off/ on reboot it...

took a leak , popped food in the oven and checked and I'm at 100% in 8? 10 mins?
I unplugged my iPhone at the start of this msg and 5 mins ltr it's still 100% battery...

other issues are that while it's plugged up recharging it gets fritzy as I type ( like this msg) and skips types multiple letters llllleeettteeerrrsss etc while I'm plugged up charging.... unplugged it's normal 🤔 ... one or the other of us is possessed I guess ...

should I replace the battery?