BuddyPress.org

@ottiya

You could add a template file named buddypress.php to your theme’s directory, and BP would use that template instead since that file is ahead of page.php in the hierarchy above.

If your theme has full-width template file for page, you can use the same to create buddypress.php

For further details, you can check https://codex.buddypress.org/themes/theme-compatibility-1-7/template-hierarchy/