Hi RZetr0,
I am Mario and I am a independent advisor, and I would like to help you.
You will need to insert the Windows 10 installation media and boot your computer from it. Once you have selected your language preferences, choose the "Repair your computer" option, followed by Troubleshoot > Advanced options > Command Prompt. From there, you can enter the command "bootrec /fixboot" to repair the boot sector or you can try using a third-party partition manager tool to repair the boot sector, or you may need to reinstall Windows.
Hope this can help you solving the issue.
Best regards,
Mário