May or sure I'm wrong there with my question

How does Kodi unmount devices?

It shows my W8.1 Laptop doesn’t disconnet proper so I can’t unmount proper from the Kodi frontend but if I umount in the lazy way:

sudo umount -l /dev/sda1

It works, may there is a solution for me to unmount proper from the frontend

Go into Video->Files and you will see any external drives listed there. Highlight the drive and press the context menu button, then choose “Safely Remove”.

Turns out it’s an usuall unmount doesn’t cut if there is something

Sorry, don’t understand what you’re saying.

Oh sorry I mean this kind of “Safely Remove” doesn’t umount the drive if there is some sort of connection from an other PC, when I use the lasy option from shell my drive is removed but not with the option from KODI

If another PC is connected to the drive via Samba then no you will not be able to unmount it until the connection is closed. This is normal because Samba maintains a lock on the drive while remote clients are connected to it. If you try to use the umount command from the command line you will find it too complains it is in use.