If you want to simply hide the breadcrumbs, wpForo already has a special option, which is located in the Dashboard > Forums > Settings > Features Tab. More info here: https://wpforo.com/docs/root/wpforo-settings/features/

If you need to some dynamic breadcrumbs I'm sorry, but I don't know any CSS code for this.

As far as I know, there is not a CSS solution. I've tried to find on the internet and nothing is found. 

You can do it only if you know js or jQuery, etc. languages

https://stackoverflow.com/questions/18998797/create-breadcrumbs-dynamically-on-client-side-using-javascript

Thank you very much, but I asked a little about something else - I wanted to remove / close bread crumbs and then restore them if necessary

Thank you for contacting us.

The CSS codes should be added in "Custom CSS code" textarea, located in the Dashboard > Forums > Settings > Styles admin page. 

More info here: https://wpforo.com/docs/root/wpforo-settings/style-settings/