Don’t be tempted to keep ‘Cleaner’ type apps running in the background. Install a good one, like Ccleaner, clean out your tablet and uninstall that app when finished. If you just want to give your tablet a quick clean to improve performance go into your settings and find Storage, then clear CACHE only. Get an SD Card, Class 1 (or 10) at least, and change settings to store pictures and other stuff there instead of on your Internal Storage. You might even be able to transfer apps you have installed to that SD Card if your settings allow for that. Certain games demand a lot of your tablets resources even when you aren’t playing them - so install an app called Greenify - this will allow you to force close multiple apps you don’t want to have running in the background while doing other things. Greenify will force close apps you preselect when the tablet goes to sleep, or when you tap on the Greenify Widget.