Custom CSS for Forums

[Fxam]

Hi,
first I’d like to say thanks for a great Plugin!

I am trying to add a forum to a website which was set up by someone else using the bbPress Plugin.
I would like to change the way the my forums are displayed without messing up the layout of the rest of the website!

I managed to use the Plugin (Custom CSS for Pages and Posts) to change the position and width of my bbPress Forum
by adding the following code the the Page used to display [bbp-forum-index]
please see: https://kwetufilminstitute.com/rmp/classes/
*/
.coursdettext, .contentholder {
width: 1000px;
float: center;
}
/*

unfortunately this only works for the root/general forum.
All other forums are still displayed:
*/
.coursdettext, .contentholder {
width: 526px;
float: left;
}
/*
as it is written in the themes styles.css!
Please see:
https://kwetufilminstitute.com/rmp/classes/forum/design-of-video-and-audio-products/

Changing the themes style.css is not an option because it would mess up the layout of other pages.

I have tried editing bbp.css with no luck and was hoping to find a simple solution using a plugin.

Anyone have any ideas? Many thanks in advance!!!

Cheers, Fxam

https://www.ads-software.com/plugins/custom-css-for-pages-and-posts/