A list of solutions are mentioned in this troubleshooting video on how to fix your Samsung device that is running slow.
00:38 Check for apps running in the background
01:42 Reboot samsung device
02:02 Optimize Samsung device
02:23 Clean up Cache Partition
02:57 Keep apps and software updated
03:23 Check for overheating
03:52 Restart to Safe mode
04:11 Factory reset
