Hi Mahtab,
Thank you for bringing this issue to our attention. Maybe these topics will help you to solve your issue as they seem to answer the same concern:
However, please note that neither of these plugins has been tested or integrated with our product.
You might require extra customization work if you wish to make them fit perfectly with your website. Unfortunately, this is a service that we do not provide.
We only share snippet only to solve issues with our theme. Any further request for CSS snippets will have to be part of a defect that needs to be fixed urgently. No snippets will be shared otherwise. As theme authors, the installation, setting or debugging of third party plugins isn’t part of the support we will provide.
To go further, we invite you to ask this question to the BuddyPress plugin authors, perhaps they will recommend you a specific plugin:
https://buddypress.org/support/
We remain available for all support requests related with the use of your theme.
Best,