Macbooc air won't boot (blank blue screen), how to fix?

Question

macbook

They brought a MacBook, asked to see what was wrong with it, they said that they tried to somehow reinstall the system on it themselves. As a result, we got the following:
When turned on, it makes a sound, it boots up with the apple logo, after which a blank blue screen appears, and the boot icon periodically appears on it, that's all. So it goes on and hangs on this blue screen. With the help of the key combinations that I found, it practically does not go anywhere, only in single-user mode it turns out.
I ask for help, because I almost never dealt with poppies at all. How can it be restored?

Answer 1

Try to hold Command + R after the reboot, there should be a recovery window.
And here is
support.apple.com/en-us/HT3964
support.apple.com/kb/PH14222?viewlocale=en_RU