Windows 10 version 2004 disk usage 100%

After I have updated to the latest version of windows 10, I have encountered some really serious problems. Whenever I do any operation on my disk (scanning my drive with an antivirus) or copying files, task manager shows 100% disk usage. I have used different antivirus softwares and I have tried every single method on the internet to solve the 100% disk usage with nothing working at all. I am sure it's not a hardware problem, but it's purely software problem. Unfortunately, I can't roll back to the previous installation of windows 10, as I have windows.old folder deleted. Will Microsoft solve this problem with this particular upgrade (version 2004) soon? Also, is there any possible way I can get version 1909 back? Maybe like a Microsoft downgrade tool or something that would download this version and I can use it instead?