Couple things to do: 1 Reboot 2 Clear RAM 3 Reinstall 4 Update every application in the Play store, especially Google. 5 uninstall non used applications for cleaning space and RAM. 6 Turn off any unused applications running in background that eating RAM. If all the above doesn't work, it could seem that you are a victim of planned obsolescence... in other words, buy new smartphone. And by buying it don't be cheapo, at least something from middle shelf and from reputable vendor like Samsung or Google.