It won’t even download

So I’m having trouble with my macbook pro - it’s only about 2 years old and the cursor keeps freezing up. All I can do is force a shutdown, as I suddenly am unable to click or type anything. So I figured I should update my Yosemite to El Capitan. But lo! I can’t even get the app to download. Sigh.

Cerebration about OS X El Capitan