I bought 2 acers swift 3 and already created 2 partitions on one of them- C: 150GB and

780GB out of 1TB. I wanted to do the same for the other laptop and weirdly under "shrink C" it only showed me around half of available shrink space:
Total size before shrink in MB: 952718
Size of available shrink space in MB: 476308
Total size after shrink in MB: 476410.
So the smallest C I can have is roughly 475GB. No extra settings or heavy usage before attempting to do it, so really brand new laptop straight after going through basic settings. I did the shrink on my old laptop with win7 and created 200GB C without any problems..
I was digging into topic and have found some tips to switch off automated managing paging file, however it's set up correctly. I tried to switch it off (without restarting computer as only got warning about performance) but it showed same numbers. When put that back to original setting, then I was asked to restart.
The information I get when I try to do the shrink is: "You cannot shrink a volume beyond the point where any unmovable files are located. See the "defrag" event in the Application log for detailed information about the operation when it has completed."
Obviously it looks as someone have reserved a shadow volume or virtual space for something and it doesn't let me pass it. I don't want to go into too complicated process but perhaps there is some silly explanation and solution to fix this. I wouldn't like to accidently lose shadow copy of disk either.
On top of that I have performed scan disk only to find some corrupt file which was repaired, but same thing happened on both laptops. And that didn't fix it. However it looks like edge CAN now download a photo, where straight after first use it was an error and instead of an image there was a broken icon with 0kb. At the same time it wasn't an issue with internet explorer. Not sure if I should run check disk and defrag?
Any suggestions and solutions?
Thanks in advance!
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