The theme you are using is most likely overriding the bbpress default template, any template files you modify in the plugin folder are most likely being bypassed by theme or child theme. It would help to visit the bbpress codex which explains the template hierarchy in detail.
Getting Started in Modifying the Main bbPress Template
Step-by-Step Guide to Creating a Custom bbPress Theme
I could try my best to help out if you could provide more information regarding which theme you are using, folder structure, child theme etc.