Don't format. As you device is old enough the applications which your are using like WhatsApp and other applications consume more RAM due to application's requirements. So you simply need to do is that: 1) Install only those app which are usefull. 2) Regular cleaning of RAM is must. (Your can do that from device manager or Device care.) 3) Restart your device once in a week. and last but not the least. 4) Keep your internal storage free above 40%
Please perform the below mentioned steps to resolve the issue:
1. Turn off Bluetooth, Wi-Fi, mobile hotspot, NFC etc to do that please swipe down on the home screen to open notification panel> Tap on Bluetooth, Location/GPS, Wi-Fi, Mobile hotspot, NFC etc, to turn off as It increases battery usage time.
2. Reduce display brightness level by swiping down on the home screen to open notification panel > Turn on Auto brightness option if available, it increases battery usage time.
3. Close background running apps, if there are any unnecessary apps running in the background as too many applications running in background may cause the battery drainage.
For further assistance, register your concern in Samsung Members Application (Open Samsung Members Application > click on “+“icon > send feedback > error report/ask questions).
