Lost space on my SSD?

I installed an NVMe M.2 512GB SSD in my laptop and wanted to install Linux next to my Windows 10. To make it easy for me, I used Windows' own disk management to reduce the volume. I reserved 40GB. In the middle of the reduction, however, the disk management is smeared for me. When I wanted to start reducing the size again I noticed that 40GB was missing when selecting how much memory I would like to release. Despite restarting, I'm now missing the 40GB in the selection and the 40 GB is also not available as allocated memory. But since the NTFS partition does not lack space, I wonder whether it is just a disk management error or whether I'm actually missing memory. Can this happen and how can I fix it?

Try Partition Wizard. The tool can do a lot more compared to the Windows 10 disk management. I've had a problem like this before.

All right, thanks for the tip