Standard Windows 10 Repair Steps ("Repair Installs") require that Windows 10 be running.
Your Windows 10 machine is not running.
So boot with a bootable (Windows) USB Key, recover your data to a USB drive.
You can try a Windows Reset (Update, Recovery, Reset), but that depends upon your Windows User Profile being good. It may be worth trying, but that is a grey area.
Otherwise format and reinstall Windows fresh is the final option.
Follow up:
If after some trial and error you are able to get Windows running, then you should consider a Windows 10 Repair Install.
Go to the Windows Media Creation Link
https://www.microsoft.com/en-us/software-download/windows10
Windows 10 is running, so click on the Download button (not Upgrade Button) and select Run. This will launch the Repair. Proceed normally answering the prompts. The default Keep prompt is to Keep Everything. Try this first.