Need a solution to a blinking screen

Based on your lack of concern if you " lose my files or software installed on Ubuntu" and the fact that you can boot Windows via " UEFI with CSM in BIOS" I would reccommend booting from a verified good live media without changing the BIOS from where it successfully boots Windows Once you have successfully booted to the verifed good live media, it would be wise to check the SMART status of your drive to rule out any hardware problem with it that could be impacting your ability to complete installation tasks. Once we have confirmed the following:

1) BIOS mode is set properly to successfully boot Windows

2) Boot into Windows and Turn Off Fast Startup The easiest way to do this is to open a Command prompt as Administrator and issue the command powercfg.exe /h off which will turn off hibernation and fast startup along with it.

2) our live media is uncorrupted

3) our hard drive is in good shape and

4) Verify that the live media is booted via EFI mode matching the mode Windows successfully boots in.

5) We have backed up everything to protect ourselves from unexpected hardware failure and operator error.

Then we can install normally as outlined here.