WebDav Windows - losing storage


i have installed Nextcloud on my Linux Server.
Everything is working, but now i want to work with my files using windows explorer.
But when i use the webdav link to install a network drive, it has the same storage capacity like my laptop-drive.
The problem is when i move files from my Nas with my laptop to the nextcloud using the network drive, i lose the amount of storage capacity also on my normal laptop drive.
Also after restart of the laptop there is less storage capacity.
How can i fix this?

I think that is not possible because you copy the files once from the source to the webdav-destination.

You can search the files on c:\ . Perhaps there is a temporally not deleted copy in a temp-dir.