You should put every HKS down (as preventative)). Power off your phone and exercise taking out your BPP-L503 battery (once out once back, after being aware that you charged your phone before to at least 60%).
Let other people pay you $100.00 “just to open and look at it” (turn around and go back home).
After above done you should proceed as described in below thread post (not before) and there you’ll realize that you have all necessary tools nearby yourself, at your disposal (your hands, your initiative, BPP-L503 battery, recommended power supply, recommended USB-C cable, red LED light (that needs to be at some particular point off).
Now, after you admit that too many “things” bothered you unnecessarily (as brand new user, which is quite understandable) proceed to this thread: Graph of the battery charge level - #12 by Quarnero.
P.S. Might be that we see us tomorrow evening (it is your turn now). Otherwise and if you are lucky please accept every helping advice from @dos only, please provide exact description every time you give some feedback to him.