Why won't it turn on or charge

OK first off

Number one problem

It randomly stops working with chargers even really good chargers

Second off

So today I had it st 31% and I was talking to my friend and it didnt turn off ot just turned on then i called her again and I saw it rapidly drop from 31% to 3% as if it was spinning I saw each number go by

I freaked out "WHOA WHOA WHOA CRYSTAL MY PHONES DYING" and I plugged it in when I plugged it in it went down to 2% so I hung up and it shut off for a hour then it finally turned on and it still said 2% I had it charging the whole time

3 hours later and it powered off once more turned on said 2% then I looked at it and just like before it rapidly went up to a 100% now I unplugged it but every half second a percentage of the battery would go down at 75% 2 mins after I unplugged it , it powered off and ive tried everything I can think off but it won't turn on

So please give me methods

I'm just a kid but I need my phone to call my family and for school work to talk to a friend or two for fun or to ask a question and its the only phone I have if it breaks I'm not getting another unless I buy it

So please answer

I'll be very grateful