Flashing folder with a question mark

Hello,

so few hours ago, my Macbook pro froze and when I restarted it, the flashing folder with a question mark showed up. I clicked cmd + r and I tried to run a first aid on Macintosh HD, but after reaching a certain point it freezes and the color wheel appears and it remain on that state forever.

I also tried to just reinstall the macOS, but it tells me that my disk is locked, and I can't enable jornaling from disk utility because that option is gray

how can I get my macbook to start? i don't even care about the stuff in it at this point :/