how to stop Mobile shutting down on apps using as Battery dropping from 70% to 0% in Android 6.0.1

**Question:- how to stop Mobile shutting down on apps using as Battery dropping from 70% to 0% in Android 6.0.1.** I have formatted my External micro sd card as internal and automatically while installing apps it moves to external sd card even Facebook and many common apps installed on micro sd card. but still many are on internal memory. i googled and founded that its may be battery calibration problem i tried to fully discharge battery to 0% by restating then again recharged it to 100% and i tried accu-battery app and many other apps for battery calibration but problem persisted of shutting down of phone at 70%- to 75% while using if its kept on standby ie. not used it sometimes dont shut down till 35% From last 2-3 days my android 6.0.1 OS mobile phone is restating even charging to 100% as its heavily used or many apps opened it just show low battery sound in main OS window to 0% and immediately shuts down. After shutting down if i charge it on black screen it shows 50%-75% battery remaining on keeping the charger on mobile when i keep the charger connected it then never gets shut down... but the mobile back panel gets heated up drastically and on seeing in accubattery app the temperature of internal sensor shows battery temp in red sign from 47 degree to 50 degree many times. I have tried in safe mode its still shutting down ...i tried in maintenance or in boot menu mode its not shut down .... now i am confused 1. is due to os android 6.0.1 crashing :- (formatted -2-3 times still occurs) 2. is it due to apps moved or installed in external micro sd card crashing ( as in safe mode it works fine dont shutdown in 36% of but apps moved installed in external card not showing in safe mode) 3. is it due to overheating of chips or circuits 4. or its due to some particular app crashing ( i tried is it due to some internal or external memory card sectors became bad due to formatting 3-5 times in this week ) 5. is battery life is finished is battery failing ( but its working fine in safe mode on common system apps) solution i think: 1. I think to format external sd card to zero level or low level formatting so that it become fresh and clear which can be done through mini partition tool 2. I think to format internal memory sd card through adb shell fstim or dd if dd if=/dev/zero of=/sdcard/filler but it doesn't make much sense on flash storage. Running fstrim to clear unused space so that it gets refreshed and any junk saved can be freshen up Any suggestions opinion are welcomed kindly give your technical expert advice for solving the issues.... Thank you in advance for reading answering and giving your precious time and precious technical advice or opinion