I am on Debian 11 and I would like to uninstall snap. This worked for every snap that was installed:
sudo snap remove name of snap
After having removed all snaps installed with I need to umount snap according to instructions. 
sudo umount /snap/core/13308
This fails due to: “umount: /snap/core/13308: das Ziel wird gerade benutzt.” meaning that snap is currently in use.
So how do I make it not being used for me to be able to umount it?
Any help appreciated. Thanks for your time.