I cant download anything on my tablet how do you fix that

You could have stated your storage systems to better evaluate the cause. However, most of the time, download failures on Androids are either caused by;

1.) Insufficient memory on download directory
2.) Firmware Errors

If the first is the case, it will help if you transfer all or few of your downloaded softwares to a higher capacity storage like your SD Card. You can find this at Application Settings on your android deveice.

If the second is the case, the best solution is to Hard Reset your Android (factory reset). You can google Hard Resetting procedure in the web. It's easy.

Hope this helps.