Your smartphone has become 4+ year old.
So it will work slow
So its right time to change device with new.
I will suggest to go for Galaxy A52 if you have budget or else go for other brands.
Still if you want to buy midrange samsung mobile then atleast take 6 GB RAM varient
Try to delete unwanted items from your mobile. Even whatsapp takes so much space from internal storage so first of all delete from files app . Buy new SD card from online store and move the files to SD storage and you can move some apps it will very helpful for you. Am using 128 class 10 memory card . .
Dear Samsung Member,
Greetings from Samsung Customer Support!
We apologize for your inconvenience. To resolve your device hanging issue please visit this link: https://www.samsung.com/in/support/mobile-devices/how-to-restart-the-device-when-freezed-or-hanged/
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Samsung Customer Support