Problem/Bug GroupManager - can't deny permission

Hi there!
I'm using GroupManagerfor my server and I also have the marriage plugin (https://www.spigotmc.org/resources/marriage-reloaded-1-15-1-8.18998/)
I want to deny a group of doing the commands of this plugin.
This is what I add to the config:
- -marry.marry
As you can see, I added "-" before and it should disable it, but it's not disabling it for a specific group, please help.
In general, I can't deny any permissions to be honest. Please help me!

It's also not working with other plugins, not only marry one..