Well if you are OK with losing any personal data on it, unless you can back that up to a computer or cloud account, you may want to try a "Hard Reset". If it is a software issue, then that should resolve it.
Now if the slowness is a hardware issue, no software changes would help.
NOTE: Doing this will clear 'all' the data on your tablet, so it is suggested you not choose this option unless you have to, or aren't worried about losing anything on the device.
Be sure you back up any data you want to keep, to a computer or cloud account, before doing the reset.
To "Hard Reset" the tablet...
1. Make sure that the tablet is actually powered off.
2. Remove your SD card, if there is one in the device.
3. Press the "Power" and the...