So my cousin was at my place and used the pc and he put the voltage power to 0,00850 or something and the memory clock to 500 or 550 after that he turned off my pc and after about a hour I turned on my pc and it’s working but it doesn’t appear anything on the screen and my mouse and keyboard are also not working. Can somebody pls help? Btw I got a ryzen 7 2700
I recommend rebooting your PC, hitting the 'delete' key multiple times until you get into the BIOS of the motherboard. Then find the section where you can reset all changes to the factory default. Save that and reboot again to see if you can get back into your operating system.
If you can't enter BIOS for some reason to do that factory reset you can try plan B