My MacBook started to get really slow recently. Now it can’t start up properly anymore. All I see is the Apple logo and then it shuts down. I've tried rebooting multiple times, but I've seen the same result over and over again.
So, I tried to reinstall my OS, but for some reason I get the error I cannot unmount my disk. And the partition seems to be locked, so I can't reinstall the OS over the internet.
Do I have a damaged disk?