What I found in the event log is some information that apparently the system was reactivated from standby mode, but I definitely shut the system down regularly. This happens all the time. What is it, some faulty ACPI config?
Since Windows 8, the shutdown is a logoff of the user + hibernation of the kernel/Windows services.
So booting is now a resume of the kernel/all drivers/services + login of an user. This resuming of services/drivers is much faster compare to a full boot where Windows has to start each service/driver again. So everything is fine. If you want the old boot/shutdown or dualboot with Linux systems, disable fast Startup.
otherwise you can't mount the Windows partition in Linux