Ok, so I've been having a bunch of problems on my MacBook Pro from 2013 with El Capitan. Everything below happened in period of a few hours. I first noticed something was wrong when I tried opening applications from my applications folder but they wouldn't open and gave me error messages. Then I tried to delete a file, but it gave me error code - 50. This happened whenever I tried to move files. I tried restarting, as I hadn't in a couple of days, but it got stuck at the apple loading screen. I then booted it in safe mode, and it worked, so I restated it again regularly. It worked, but I still couldn't open any applications, including safari and chrome. I ran first aid on my disk, and it said everything was normal. I restarted again, but this time, a prohibitory symbol (circle with a line through it) appeared in place of the apple symbol. This happened every time I booted, even in safe mode. So then I booted in recovery mode and tried reinstalling OS X. However, when the progress bar reached the end, it just went back to the recovery mode home screen. I knew something was wrong so I tried to erase and resintall my hard drive. I went to disk utility, selected Macintosh HD, clicked erase, and set the name to Macintosh HD and format to OS X extended (journaled). But then, "Erase process has failed" and "could not mount disk0s2 with name (null) after erase." Does anyone have an idea why this would happen or have any suggestions? I am still in high school so taking it to apple would be my last resort.