My phone screen is dark because the lights are off

azzel, can you clarify your question? It may be a translation issue, but it sounds to me as though you're saying that the LCD's backlight has failed. Is that what you mean when you say the lights are off?

If that's the case, your best bet to fix the problem is to replace the screen. I know on some older iPhones it was sometimes possible to replace a bad backlight, but it's difficult; for one thing parts like that are hard to come by and guides are non-existent. So the only practical option is a new screen.

Fortunately, iFixit has just the guide you need to replace the display assembly, consisting of the LCD, backlight and digitizer.

Xiaomi Redmi Note 8 Screen Replacement - iFixit Repair Guide