Displaying/separating categories and forums in usual way

Hello,

I ask your comprehension, I’m not fluent in english (I’m french). I’ll try to explain myself the best way I can.

I’m using BBpress and I want to display categories in the normal/usual way in my index forums : Categories separating forums and forums forming lines in the index. Actually, categories display like forums and forums display like subforums : https://operationarcheo.fr/forum/

I want to have categories separating forums like this : https://drive.google.com/file/d/1icL0s-0vcRuPvX4uVNyluI_INMepC0-G/view?usp=sharing

I’m searching the simplest way to do this. Please consider that I’m not developper and also have difficulties to use english documentation.

Thank’s,

Mathieu

PS :
– Theme : Customizr free version
– WordPress version : 4.9.4
– BBpress version : 2.5.14